Slack slash commands

## What does this MR do?

Implement Slack Slash Commands by utilizing generalized Mattermost presenter to fulfill Slack requirements.

## Why was this MR needed?

We want to expose Slack Slash Commands as a first-class service.

## What are the relevant issue numbers?

Supersedes !8007  
Closes #22182

See merge request !8126

Align milestone column header with count number

## What does this MR do?
- Aligns the milestone column header with the count number
- Prevents the count from wrapping below the column header

## Why was this MR needed?
- Count number was being pushed below the column header text if the text was too long

## Screenshots (if relevant)
- see issue sceenshots for before #25810 
- fixed version
![milestones](/uploads/ca12c290abe814b457ad3b2fb86f7696/milestones.png)


## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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 it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #25810

See merge request !8177

Update font size of detail page header to 14px

Before:    
![Screen_Shot_2016-12-19_at_2.55.08_PM](/uploads/ff1544631ff376c3039674ac45eec696/Screen_Shot_2016-12-19_at_2.55.08_PM.png)
After:   
![Screen_Shot_2016-12-19_at_2.54.48_PM](/uploads/8a1038cc851e186eddada625b8c8de83/Screen_Shot_2016-12-19_at_2.54.48_PM.png)

Closes #25735

See merge request !8183

Remove inline-block styling from status

Before:   
![Screen_Shot_2016-12-19_at_2.13.42_PM](/uploads/2bb7bc84f97fb3489854518e35349203/Screen_Shot_2016-12-19_at_2.13.42_PM.png)
After:   
![Screen_Shot_2016-12-19_at_2.12.34_PM](/uploads/d228c105f90d546fce5b1653d7a74fd7/Screen_Shot_2016-12-19_at_2.12.34_PM.png)

See merge request !8181

Give forbidden if project for the build was deleted

I guess we don't need a change log entry because this is just for an internal corner case fix.

Closes #25309

See merge request !8091

Fix Route#rename_children behavior

## What does this MR do?

Fix Route#rename_children behavior.
Given group `gitlab` and `gitlab-org` exists. When rename `gitlab` it
will rename `gitlab-org` group route too. This MR fixes it

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/2772

See merge request !8182

Even out padding on "plus" button in breadcrumb menu

Changed the padding on the ```+``` button to be ```6px``` on all sides.

![Screen_Shot_2016-12-16_at_8_06_07_PM](/uploads/cc85f8ff36c7d2dd75546a67445af19a/Screen_Shot_2016-12-16_at_8_06_07_PM.png)

Closes #25740

See merge request !8154

Add Wiki import to BB importer

## What does this MR do?

Adds wiki importing



- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/25819

See merge request !8180

Add LDAP maintenance task

I've received quite a few support requests where a user has renamed their LDAP server in the configuration file. This causes lots of issues where users are suddenly unable to sign in. It's easy enough to fix through the Rails console, but each time I had to instruct users how to get to the Rails console and what to type. This Rake task takes care of this and updates from old to new provider automatically.

Example: `sudo gitlab-rake gitlab:ldap:rename_provider[ldapmain,ldapcustom]`

cc/ @patricio @balameb Do you think this is useful?

See merge request !2181

Changed plus button padding to 6px 10px

[ci skip]

[ci skip]

Move Admin Appearance spinach feature to RSpec

Part of #23036

See merge request !8063

Move buttons to project header

Closes #25692    
Before:   
<img src="/uploads/fb65f1ca8021f1669071a3980e5f8258/Screen_Shot_2016-12-14_at_3.52.19_PM.png" width="800px">
After (with Koding setup):   
<img src="/uploads/236e0103186a1b482c4302aa3a4b94b1/Screen_Shot_2016-12-16_at_10.09.53_AM.png" width="800px">
After (without Koding setup):
<img src="/uploads/04bc8360831c98a4c86d3b11ee24826d/Screen_Shot_2016-12-16_at_10.18.35_AM.png" width="800px">


See merge request !8095

Given group `gitlab` and `gitlab-org` exists. When rename `gitlab` it
will rename `gitlab-org` group route too. This commit fixes it
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Make CI badge hitboxes better match container

## What does this MR do?

Makes the Pipeline graph badge hitboxes accurately match their containers.
Currently, there's an issue where the badge highlights, as though, it's clickable, but clicking it does nothing:

![before](/uploads/668f841c640bc586044c89bed9f1e1e9/before.gif)

This is due to the `<a>` and `<button>` elements being padded into the parent elements. So, the parent would react to a cursor, but the cursor wouldn't be on the `<a>`/`<button>` yet.

![before-hitbox](/uploads/6ebaaa4be1096fbfc37f8d73da492c7b/before-hitbox.png)

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

Maybe the tests? I kept the style changes as minimal as possible.

## Why was this MR needed?

I was annoyed every time I clicked on a badge that I was _clearly on_ (it highlighted), but nothing happened.
If I found it irritating, perhaps someone else did too.

## Screenshots (if relevant)

How it behaves in the PR:
![finished](/uploads/c26fabe37ccf17f171f40b48522702b2/finished.gif)

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- Tests
  - [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] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes #25547 

See merge request !8156

Move admin broadcast messages spinach feature to RSpec

Part of #23036

See merge request !8067

Backport changes from EE to gl_dropdown.js

REF: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/977

See merge request !8165

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8091#note_20253762

Convert CI YAML variables keys into strings

So that this would be more consistent with the other variables,
which all of them are string based.

Closes #25554

See merge request !8088

Fix import/export merge requests error

When MWBS is set and the MR exported/imported an error gets thrown. We should ignore this so it can succeed as the merge user may no longer exist in the target instance.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/24009 and https://gitlab.com/gitlab-com/support-forum/issues/1345

See merge request !8134

Fix missing service error importing from EE to CE

Ignores services that are missing in the new instance (EE or even a customised instance), to avoid breaking the import.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/23782

See merge request !8144

Fix 500 error for invalid path when visiting blame page

Closes #25761

See merge request !8145

Bump gitlab-shell to 4.1.1

This fixes a compatibility issue with Git 2.11 (#25301):

- [x] gitlab-shell MR: gitlab-org/gitlab-shell!112
- [x] CE MR: !7967
- [x] EE MR: gitlab-org/gitlab-ee!964

See merge request !8143

Signed-off-by: Rémy Coutable <remy@rymai.me>

Move admin labels spinach test to RSpec

Part of #23036

See merge request !8166