Render relative timestamps for all commits in projects commit list

fixes #15366 

See merge request !3821

Removed commented text from system notes

![Screen_Shot_2016-04-20_at_14.49.22](/uploads/b1617af49cc35595afd6dfcf761a775c/Screen_Shot_2016-04-20_at_14.49.22.png)

See merge request !3836

Fixed issue with new MR form layout

Currently it is all over the place:

![Screen_Shot_2016-04-20_at_14.59.48](/uploads/09c3dffc2138140e3b009ab2564f0aca/Screen_Shot_2016-04-20_at_14.59.48.png)

Now:

![Screen_Shot_2016-04-20_at_14.59.44](/uploads/ef5ba8b7393253ecb732c57ba37dd0cf/Screen_Shot_2016-04-20_at_14.59.44.png)

See merge request !3837

Fixes issue with note form inheriting text color

It was only really noticeable on dark themed diffs

![Screen_Shot_2016-04-20_at_14.44.58](/uploads/4f32b487de7e4c09a494dc3c8c767ece/Screen_Shot_2016-04-20_at_14.44.58.png)

See merge request !3834

Verify the MR being displayed question has a merge commit set and can be cherry-picked

See merge request !3830

Add incremental build trace update API

Closes #14537 

Must be merged if we want changes from gitlab-org/gitlab-ci-multi-runner!124 to work.

See merge request !3447

[ci skip]

[ci skip]

[ci skip]

add slack notifications for wiki pages

## What does this MR do?

Lets the Slack service be configured to send notifications when wiki pages are created or edited.

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

I'm just starting to get familiar with the Gitlab codebase and I was unsure on how to get the wiki page url to pass it to the slack message, on whether or not I needed to refactor the create/update methods for wiki pages from the controller to a service (but seemed necessary to test it better), and if I needed to add a column to the web hooks table or if the services table would have been enough. Please let me know if I should change anything and I will improve the MR, thanks for checking :)

## Why was this MR needed?

Related to #563 and fixes #4233.



See merge request !2998

Add raw build trace output

Closes #15308, #15147

Changes in the UI:

- on finished build:

    ![raw-on-finished-build](/uploads/0e0904940db5b381ae064d49343c6508/raw-on-finished-build.png)

- on running build:

    ![raw-on-running-build](/uploads/0e4c800b68c12bdd0cbd2eea732b22ff/raw-on-running-build.png)

See merge request !3767

License templates when creating/editing a LICENSE file

Closes #12804

See merge request !3660

update changelog

Fix javascript errors with invalid json because of commas

fixes #15390 

See merge request !3827

[ci skip]