Mutliple label filter

Fixes #989 

See merge request !3438

Removed duplicate ID's from the HTML



See merge request !3818

Update changelog



See merge request !3801

fix bug causing the infinite scrolling in activity feeds to break when you click a link and navigate back

![arrg_](/uploads/53b2a01d3b55938cc12c805e1a81ff6b/arrg_.gif)

See merge request !3835

Discussion note icon shows up when you click on diff on touch screen

Fixes #15104 

* Fix bug that stopped discussion note button from showing up on iOS
* Shifted button a few `px` to fix slight cutoff
<div>
<img src="/uploads/9d507091f33aa69ef68323386bf3a5c2/Screen_Shot_2016-04-15_at_12.08.46_PM.png" width="300px">
<img src="/uploads/a964a2a46636cbe4593abf272b5796f7/Screen_Shot_2016-04-15_at_12.11.40_PM.png" width="300px">
</div>

See merge request !3755

fix bug causing the infinite scrolling in activity feeds to break when you click a link and navigate back

Backport select_helper from EE



See merge request !3825

Fixed issue with no label not working correctly

Fixed issue with sidebar edit links toggling anchor

This caused an issue with the page scrolling from the bottom to the top. Also stopped the dropdown links doing the same.

See merge request !3819

Render relative timestamps for all commits in projects commit list

fixes #15366 

See merge request !3821

Created issuable singleton to house the filtering

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

get the multi filter labels feature to work on merge request, also escape characters in the templates to prevent xss attack

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