Project services and JIRA documentation clean up

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/176

This was first aiming to fix the JIRA references to EE, but as I was going through it, I decided to revamp more.

@Haydn once merged here and then Valery merges CE into EE it should be fixed in doc.gitlab.com as well.

@dblessing the docs state that we support JIRA 6.x. I see that 7.x is out, should the docs be amended? Also we seem to have a place to document services (http://doc.gitlab.com/ce/project_services/project_services.html), but the JIRA doc is under integration :/ I'd like it to have it moved under `project_services/`, but I guess most customers know the current URL better.

See merge request !2345

[ci skip]

See merge request !2346

Delete tag via API

### What does this MR do?

Implements deleting a tag via the API.

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

On success, it returns the name of the deleted tag. This is similar to the [delete branch API](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/api/branches.rb#L111).

###  What are the relevant issue numbers / Feature requests?

* This MR closes #1575 
* Closes http://feedback.gitlab.com/forums/176466-general/suggestions/6599203-delete-tags-through-the-api

@stanhu Could you do a review?

See merge request !1862

This ensures CurrentSettings#connect_to_db? returns "false" in the event
of a database not existing, instead of raising an error.

- new images where needed
- move images to a separate img directory
- use table for the service fields
- link to new documents

[ci skip]

Accept 2xx status codes for successful Web hook triggers

Closes https://github.com/gitlabhq/gitlabhq/issues/9956

See merge request !2332

changes titles

Fixes #5909

See merge request !2334

adds reference to the bottom of sidebar

Fixes #4183 
![Screen_Shot_2016-01-07_at_3.17.32_PM](/uploads/8d71b475f1775d555cf5898921e86a1d/Screen_Shot_2016-01-07_at_3.17.32_PM.png)


See merge request !2339

css change to height to make gray container fit

Fixes #5893 
![Screen_Shot_2016-01-07_at_1.22.53_PM](/uploads/7bdd44a71d255fa1439e5b96af0bd48b/Screen_Shot_2016-01-07_at_1.22.53_PM.png)


See merge request !2337

[ci skip]

Update project services to include all supported ones

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/80

See merge request !2297

Remove stamp gem

Closes #5908

See merge request !2323

Give credit to user who created find file feature

[ci skip]

See merge request !2342

[ci skip]

Closes #5908

Properly set task-list class on single item task lists

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4193

See merge request !2330

Update Gemfile.lock

My Bundler didn't agree with the previous order.

See merge request !2331

Link to milestone in "Milestone changed" system note

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4141

See merge request !2203

Annotate models

Time to refresh the comments via `annotate`.


See merge request !2311

fixes ajax issue with issue spec



See merge request !2333

Ajax filter commits

Fixes #3509 

![Screenshot_2016-01-06_13.07.53](/uploads/7400d855d8207e37e3c0ec09cb2265e9/Screenshot_2016-01-06_13.07.53.png)


See merge request !2314

Closes https://github.com/gitlabhq/gitlabhq/issues/9956

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>