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

Add a fallback for Safari copy-to-clipboard

Also, hide the tooltip in a less stupid way.

Closes #3547

See merge request !1844

Commits without .gitlab-ci.yml are marked as skipped

- Commits without .gitlab-ci.yml are marked as skipped
- Save detailed error when YAML syntax

This also fixes: #3521 #3546 

/cc @jacobvosmaer 


See merge request !1827

Award Emoji

This it first iteration of award emoji feature.
We have plan to extend emoji picker by the next release.

For now, you can add award by clicking to the emoji picker or posting a regular comment with emoji like "👍" and any other. You can post not only emoji that listed in the emoji picker.

See merge request !1825

Add missing dot in confirm modal



See merge request !1645

Also, hide the tooltip in a less stupid way.

Closes #3547

Improve performance of finding issues with/without labels

The changes in this MR ultimately lead to finding issues with(out) labels being about 2x faster due to:

1. Newly added indexes on `issues.state` and `projects.visibility_level`
2. Adjusting the query so that finding issues for multiple projects is more efficient

See merge request !1787

Improve personal snippet access workflow.

Replaces !1709

Fixes #3258

See merge request !1817

Add option to create merge request when editing/creating a file

Replaces !1611 

Fixes #3059

See merge request !1820

Fix 'Attach a file' link in new tag form

Also removed a little bit of code repetition :)

See merge request !1834

Update gitlab-shell documentation to 2.6.7



See merge request !1836

Do not limit workhorse POST/PUT size in NGINX

Limiting, if any, should happen in gitlab-workhorse.

See merge request !1831

Add link to git-lfs client  [ci skip]



See merge request !1832

Fix bottom position of scroll buttons in build log page

Look at the up/down buttons as well as the **Enable Autoscroll**.

The **Enable Autoscroll** could also be alligned with the right grey box.


## Before

![autoscroll_before](/uploads/f410dc353ca66c338d8a29c7c294758a/autoscroll_before.png)

## After

![autoscroll_after](/uploads/015fdf53618a0d6f468d666de1bbab6a/autoscroll_after.png)


\cc @dzaporozhets @creamzy 

See merge request !1792

Limiting, if any, should happen in gitlab-workhorse.

Deploy page should be shown for all pages not just root

Related to change already merged to Omnibus - gitlab-org/omnibus-gitlab!540

This change makes it so the deploy page is shown on all GitLab pages if the page exists. Users will no longer receive the 502 when deploys are happening.

See merge request !1828