Add upvote/downvote fields to merge request and note API to preserve compatibility

As discussed in !1825 we should not break the API compatibility.

* This MR adds the fields `upvotes`/`downvotes` to the merge request API again, which always return `0`.
* Add the fields `upvote`/`downvote` to the notes API, which always return `false`

This behavior is documented in the API docs.

See merge request !1867

Make tag API for release feature consistent

Make tags API consistent with other tags methods. This changes the endpoint from `PUT /projects/:id/repository/:tag/release` to `PUT /projects/:id/repository/tags/:tag_name/release`.

On thing the API is still missing, is an error if the tag does not exist. Right now it returns 200 even the tag does not exist. I'll fix that such it returns 404.

@stanhu Can you review?
@rspeicher This MR should go into 8.2

See merge request !1864

Fix CI yaml syntax documentation [ci skip]



See merge request !1866

Award Emoji: fix for merge requests

Closes #3597

See merge request !1865

[ci skip]

Remove accidentally added line.

Reference: #3598 

See merge request !1858

Use award emoticons in GitLab workflow

Remove the old voting slides and use the emoji bar.

[ci skip]

See merge request !1863

Add tags page to readme

The tags page was separated for the release feature but not to the index readme.

[ci skip]

See merge request !1861

Handle removed source projects in MR CI commits

Fixes #3599 

@dzaporozhets assigning this to you since you wrote the original code. Perhaps checking for the source project isn't the right way, but I'm not sure if there's a better way (e.g. somewhere earlier in the process) that we can detect this.

See merge request !1859

Port GitLab EE ProjectsFinder changes

These changes were added in GitLab EE commit
d39de0ea91b26b8840195e5674b92c353cc16661. The tests were a bit bugged
(they used a non existing group, thus not testing a crucial part) which
I only noticed when porting CE changes to EE.

See merge request !1854

Reduce method complexity in AutocompleteController

Backport of gitlab-org/gitlab-ee!58

See merge request !1833

When calling MergeRequest#ci_commit the code would previously raise an
error if the source project no longer existed (e.g. because the user
removed their fork).

See #3599 for more information.

It should exist in EE only.

fix syntax error in common.scss

Fix a syntax error.

See merge request !1857

Fix Drone web hook URL not being updated

Fixes regression of !1774: fixes Drone Web hook for both service templates and project services.



See merge request !1856

These changes were added in GitLab EE commit
d39de0ea91b26b8840195e5674b92c353cc16661. The tests were a bit bugged
(they used a non existing group, thus not testing a crucial part) which
I only noticed when porting CE changes to EE.

Bump GitLab Workhorse version to 0.4.2



See merge request !1830

Add support for batch download operation

- Drops Accept for all download requests,
- Allows to do batch download for public projects and non-authorized users
- Returns 501 for legacy API with message to upgrade the client

/cc @marin @jacobvosmaer @yorickpeterse 

See merge request !1842

Fix for Emoji



See merge request !1849

Lfs default and backup

Part of gitlab-org/gitlab-ce#2955

See merge request !1823

More GitLab spellings. No dedicated CI in omnibus



See merge request !1838

Update LFS docs for cloning

Cloning the repo already downloads the LFS tracked files.

See merge request !1839

Add clipboard button to merge request cross-project reference

See merge request !1847