Restrict public users for private instances

Implements #3508

See merge request !3440

Count the number of SQL queries per transaction

cc @pcarranza 

See merge request !3783

Fixed issue with tasklist toggling sidebar refresh

Closes #15270

See merge request !3782

Added loading icon to import buttons

See #14488 for more details

See merge request !3662

Print style

[test.pdf](/uploads/0dab5c1b2d0c4d0cd7e8930e9b660a9f/test.pdf)

Closes #14201

See merge request !3784

Discussion notes update

- At the moment discussion notes are rendered in a list but arent actually a list item and that can cause overflow issues
- Moved the dates to be in the header like other notes
- Fixed overlapping issue on mobile

See merge request !3720

Fixes gitlab-org/gitlab-ce#15335

Add environment variables on a job level in CI

Make it possible to define environment variables on a job level.

Closes #14716

See merge request !3612

Scroll to the last comment I made and edit it.

Pressing up in an empty comment box will edit your last comment. 

Also now when you click edit on a comment it will put the cursor at the end.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15267

![scrollup](/uploads/b056fdc479d39311f2be412458028a83/scrollup.gif)

See merge request !3757

At this point this is being handled by GitLab Runner and we need to
introduce this as a separate merge request.

Instrument Repository.clean_old_archives

This is done so we have some metrics for https://gitlab.com/gitlab-org/gitlab-ce/issues/15256.

See merge request !3742

Closes #14201