Fix error when CI job variables key used but not specified

## What does this MR do?

This MR fixes a an error when CI job variables specified, but not defined:

```yaml
image: ruby:2.2

test:
  variables:
  script:
     - rspec
```

## What are the relevant issue numbers?

Closes #18764  
Follow up discussion in: #18775 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4745

Make sure that artifacts_file is nullified after removing artifacts

## What does this MR do?
Fixes a problem that `ExpireBuildArtifactsWorker` is executed for all previously removed artifacts.

## Why was this MR needed?
Currently the `Ci::Build::erase_artifacts!` doesn't ensure that data are saved to database.
The bang at end of this method lets you believe that it should do so.
This adds a missing `save` to this method.

## What are the relevant issue numbers?
None, yet.

## CHANGELOG
Since this is regression in feature introduce in RC4 no CHANGELOG entry is needed.

cc @grzesiek 


See merge request !4741

Validate only and except regexp

## What does this MR do?
Adds a better validation for only and except which can contain regexps.

## Why was this MR needed?
Currently the RegexpError can be raised when processing next stage which leads to 500 in different places of code base.
This adds early check that regexps used in only and except are valid.

cc @grzesiek 

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4736

Allow creating Personal Access Tokens through the website

Related to #2979 

- Allow a user to create personal access tokens, and use them to authenticate
- Refactor `API::Helpers` into `API::Helpers::Core` and `API::Helpers::Authentication`

# Tasks

- [ ]  #2979 (!3749)  - Personal Access Tokens
    - [x]  Basic Implementation
        - [x]  Add UI to add "Personal Access Tokens"
        - [x]  Reload `lib/api` on every request
        - [x]  Respect these tokens for API requests
        - [x]  Just a param or a header too?
        - [x]  Allow revoking tokens
        - [x]  Expire tokens
        - [x]  Left bar should have a "PAT" icon
        - [x]  Scopes?
        - [x]  Copy to Clipboard
        - [x]  Show active/inactive tokens separately
            - [x]  No need to check for expired/revoked in the appropriate places
        - [x]  Why does regular ApplicationController check for private token?
        - [x]  Support non-API requests
        - [x]  Revert (or work on) `lib/api` eager loading
    - [x]  Create MR
    - [x]  Refactoring
    - [x]  Fix tests
    - [x]  Write more tests
    - [x]  Add screenshots to MR
    - [x]  Add description of query performance to MR
    - [x]  Limit the number of queries in the `personal_access_tokens` page
    - [x]  Wait for CI to pass
    - [x]  Fix merge issues in schema.rb
    - [x]  Assign MR to endboss
    - [x]  Wait for feedback
    - [x]  Fix feedback
        - [x]  Wait for CI to pass
    - [x]  Assign to @rspeicher
    - [x]  Fix @rspeicher's comments
    - [x]  Wait for CI to pass
    - [x]  Assign back to @rspeicher
    - [x]  Write documentation and ping @axil
    - [x]  Wait for Axil to respond
    - [x]  Assign to endboss
    - [x]  Address Douwe's feedback
        - [x]  Use the `private_token` or `authentication_token` param instead of `personal_access_token`
        - [x]  Ditto for the header
    - [x]  Assign to endboss
    - [x]  Make sure CI is green
    - [x]  Address Douwe's feedback
        - [x]  Don't go through the `authenticate_user_from_private_token!` method, if a private token is supplied (or combine them)
        - [x]  In `authenticate_user_from_personal_access_token!` don't hit DB if `token_string` is `nil`
        - [x]  Use `current_user.personal_access_tokens.build` in the controller
        - [x]  Remove the "We aren't using `personal_access_token` as the root param" comment
        - [x]  `No need for = "...", we can just have the Inactive ... #{...} on the next line` in the view
        - [x]  Render dates in a (more) human format
        - [x]  CSS issue with table
        - [x]  Don't show the tokens in the UI indefinitely
        - [x]  How to implement scopes? Add-on to current impl? Doorkeeper?
    - [x]  Wait for @DouweM's comments about scopes
    - [x]  Address @DouweM's second review 
        - [x]  Try not using `native['innerHTML']`
        - [x]  use contexts for all "when ..."
        - [x]  Ensure consistency (styling) with other pages for "You don't have any tokens" message
        - [x]  "Actions" table column doesn't need a label
        - [x]  %td can be moved outside of the if/else statement
        - [x]  The header title should be "Profile Settings"
        - [x]  Can this be a `before_create`, so we don't need to use `generate`?
        - [x]  If it couldn't be revoked, will we show an error?
        - [x]  If it couldn't be saved, will we show an error?
    - [x]  Merge master
    - [x]  Update CHANGELOG entry
    - [x]  Add tests for form errors?
    - [x]  Post screenshots
    - [x]  Tag @jschatz1 for review
    - [x]  Wait for [build](https://gitlab.com/gitlab-org/gitlab-ce/commit/0dff6fd/builds) to pass
    - [x]  Respond to @jschatz1's comments
        - [x]  Hardcoded colors should be variables
        - [x]  Should not be allowed to chose a date in the past
        - [x]  Use the same table as in the Applications tab
        - [x]  button should say "Create Personal Access Token"
        - [x]  Float the revoke to the right on the `a`
        - [x]  Change revocation message. "Are you sure you want to revoke this certificate? This action cannot be undone."
        - [x]  Date stays selected and looks selected even though date is set as "never".
        - [x]  ~~hover on the calendar button shifts~~ (not caused by this MR - happens on `milestones#new` as well)
        - [x]  Don't use the panel for the created token
            - [x]  Use a normal flash for "Your new personal access token has been created"
            - [x]  Show the input (with the token) below it full width.
            - [x]  Put the "Make sure you save it - you won't be able to access it again." message near the input
        - [x]  Have the input highlight all on single click
    - [x]  Update screenshots
    - [x]  Merge master in + conflicts
    - [x]  Assign to @jschatz1 again
    - [x]  Respond to @jschatz1's comments
        - [x]  No button for clipboard, only link
        - [x]  text-danger
        - [x]  highlight fade on that area where the token was created
    - [x]  Make sure [build](https://gitlab.com/gitlab-org/gitlab-ce/commit/d754d99179f1ffe846fcc1d8e858163b39efc5dc/builds) is green
    - [x]  Assign to @jschatz1
    - [x]  Wait for [build](https://gitlab.com/gitlab-org/gitlab-ce/commit/faa0e3f7580bc38d4d12916b4589c64d6c2678a7/builds) to pass
    - [x]  Respond to @DouweM's feedback
        - [x]  move the redirect_to out of the if/else
        - [x]  certificate -> token
        - [x]  datepicker back to text field
        - [x]  combine the get_user_from_private_token and get_user_from_personal_access_token methods in ApplicationController
        - [x]  combine the get_user_from_private_token and get_user_from_personal_access_token methods in `lib/api/helpers`
        - [x]  don't need the new constants
    - [x]  Wait for [build](https://gitlab.com/gitlab-org/gitlab-ce/commit/9d7cda3ddce52baad9618466a5d00319b333be57/builds) to pass
    - [ ]  Wait for merge

# Screenshots
![Screen_Shot_2016-06-16_at_8.30.33_AM](/uploads/30a168964b7c5e0eb322705747829fb6/Screen_Shot_2016-06-16_at_8.30.33_AM.png)
![Screen_Shot_2016-06-16_at_8.30.44_AM](/uploads/7a8202885df6120071bbe81b215aaead/Screen_Shot_2016-06-16_at_8.30.44_AM.png)
![Screen_Shot_2016-06-16_at_8.31.02_AM](/uploads/6905c0848864e390138b771389c7a1b2/Screen_Shot_2016-06-16_at_8.31.02_AM.png)
![Screen_Shot_2016-06-16_at_8.31.29_AM](/uploads/0bc92369fb2f9bc335773f6abec421c3/Screen_Shot_2016-06-16_at_8.31.29_AM.png)

See merge request !3749

Fixed styling of commit box in new MR

## What does this MR do?

Fixes an issue that caused the new merge request commit box to go all funny styled.

## What are the relevant issue numbers?

#18781 

## Screenshots (if relevant)

![Screen_Shot_2016-06-17_at_14.08.44](/uploads/b1e34b0c6bf67adc1be8748306e20b06/Screen_Shot_2016-06-17_at_14.08.44.png)

See merge request !4747

Closes #18781

Currently the RegexpError can be raised when processing next stage which leads to 500 in different places of code base.
This adds early check that regexps used in only and except are valid.

Use Git cached counters on project show page

See merge request !4711

Customize all Devise mails

Continuing from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3354

See merge request !4297

[ci skip]

Remove JiraIssue model and replace references with ExternalIssue

This MR Removes unused JiraIssue class and replaces references with ExternalIssue

Closes #18203 

See merge request !4659

Add GFM autocomplete for labels

Closes #14637 

See merge request !4013

Fixed ordering in Project.find_with_namespace

This MR fixes the ordering of `Project.find_with_namespace` to ensure that it returns rows that match literally first.

Closes #18603

See merge request !4682

Use gitlab-git 10.2.0

Closes #18741

See merge request !4722

Reduce SQL query counts in IssueReferenceFilter

## What does this MR do?

This MR adds a preparation phase for reference filters that allows them to prepare/create data structures used while iterating over HTML nodes. In this particular case the preparation phase is used for issue references to greatly cut down the amount of queries executed to get projects/issues for Markdown references.

## Are there points in the code the reviewer needs to double check?

No.

## Why was this MR needed?

Rendering Markdown containing issue references would run at most two queries for every issue reference: one to get the project and one to get the issue from said project. When rendering Markdown with lots of issue references this would result in _a lot_ of queries being executed.

## What are the relevant issue numbers?

#18042

See merge request !4410

Added title attribute to entries in tree view

## What does this MR do?

Adds a title attribute to entries in the tree view. Moe useful when files have long names.

## What are the relevant issue numbers?

Closes #18353 


See merge request !4709

Added source branch text to dropdown toggle

## What does this MR do?

Previously, the dropdown toggle would default to "Select source branch", this changes that so that it defaults to the branch name and if that doesn't exist, it defaults to "Select source branch"

## Screenshots (if relevant)

![Screen_Shot_2016-06-07_at_12.20.10](/uploads/40d31e21297a99300050cf9f23bd7371/Screen_Shot_2016-06-07_at_12.20.10.png)

See merge request !4504

Fix project header alignment media query bug

## What does this MR do?
Fixes media query bug on project header

## Screenshots (if relevant)
![Screen_Shot_2016-06-15_at_3.22.20_PM](/uploads/3d84f8ffb88c316f317048e15ffea4f3/Screen_Shot_2016-06-15_at_3.22.20_PM.png)

See merge request !4689

Add bottom padding for merge request command line text

Because without bottom padding text is too close to the UI tabs - hard to navigate



See merge request !4681

Avoid a TypeError when initializing MergeRequest JS class with no arg

## What does this MR do?

Avoid a TypeError when initializing MergeRequest JS class with no arg.

## Are there points in the code the reviewer needs to double check?

No.

## Why was this MR needed?

Without this sane default you would get the following error when you
tried to instantiate a new MergeRequest object with no argument (i.e.
`new MergeRequest();`):
    
    TypeError: undefined is not an object (evaluating 'this.opts.action')

## What are the relevant issue numbers?

Fixes #13525.

## Does this MR meet the acceptance criteria?

- [x] No CHANGELOG since it's a trivial internal change
- [x] Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4667

Fixed alignment of download dropdown

## What does this MR do?

Correctly aligns the download dropdown on merge requests

## Screenshots (if relevant)

![Screen_Shot_2016-06-14_at_14.47.06](/uploads/9381f25110e5573e56aa5c3f46786df5/Screen_Shot_2016-06-14_at_14.47.06.png)

See merge request !4646

Fixed last push event banner not being in container

## What does this MR do?

Adds the last push event content into a container with the correct class.

## What are the relevant issue numbers?

Closes #18567 

## Screenshots (if relevant)

![Screen_Shot_2016-06-14_at_13.17.41](/uploads/4afa3d2c73e59c5ffbd53869e49baa92/Screen_Shot_2016-06-14_at_13.17.41.png)

See merge request !4644