Improve UX in build artifacts browser

This improves UX in build artifacts browser, and makes it more consistent with repository tree browser we already have.

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Before:

![ux_artifacts_before](/uploads/9869ff74afd5e6636f0df81c7823fb6f/ux_artifacts_before.png)

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After:

![ux_artifacts_after](/uploads/cdb68925f4489bb852fd701870e6d6a0/ux_artifacts_after.png)

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It is easier to click on a file/directory entry now, because we don't need to click on a entry's basename (that can be really short, like `..` parent directory). We also show `Compressed to` size that indicates how much storage does this entry really consume.

Row for an entry is also highlighted on hover and we do not have Download button (clicking on a file row / file basename is enough to download a file).

Closes #10242 

See merge request !2477

Remove leading comma when user is the only one to award that emoji

Fixes #9073

See merge request !2450

Use gitlab-workhorse 0.6.0

[ci skip]

See merge request !2483

Ensure Gravatar host looks like an actual host

Solves #10243.

I've chosen to simplify the method that extracts the host: since we
only need the host, let's get rid of the path and thus get rid of the
escaping problems!

Unit tests should ensure that most of the cases are covered.

See merge request !2482

See merge request !2481

See merge request !2480

See merge request !2479

When using IssuableFinder with a Group we can greatly reduce the amount
of projects operated on (due to not including all public/internal
projects) by simply passing it down to the ProjectsFinder class.

This reduces the timings of the involved queries from roughly 300
ms to roughly 20 ms.

Fixes gitlab-org/gitlab-ce#4071, gitlab-org/gitlab-ce#3707

Document new API pagination headers

Document new API pagination headers introduced in !2426. Solves #8098.

/cc @dzaporozhets @dblessing

See merge request !2435

- Fix heading names
- Fix curl example
- Use full request output
- Use table for the extra headers

update

old
![Screenshot_2016-01-14_22.46.52](/uploads/d165897a6118c4b276e6b53982077cb5/Screenshot_2016-01-14_22.46.52.png)

new
![Screenshot_2016-01-14_22.46.21](/uploads/6b34cd8b1a2799506676103fcbc80450/Screenshot_2016-01-14_22.46.21.png)


See merge request !2441

Raise hook url limit

1. Up varchar url limit to 2000 chars instead 255
2. Maybe migration?
3. 255 characters - it is not enough
4. nil
5. nil

See merge request !1940

Removes white line when hiding diff comments in MR

Fixes #6071 

See merge request !2407

Fixes issue where firefox does not delete message after comment submit

Issue was **not** in the way comment was being submitted.
`app/assets/javascripts/awards_handler.coffee` was throwing an error.
This error was preventing any js from running after it.
Fixes #1473

See merge request !2452

Use a more sensible message for the AbuseReport uniqueness validation

Previously it was "user has already been taken", when really we were
saying the user has already been reported.

See merge request !2461

Fixes #9073

Issue page keeps jumping up

This happens when the discussion side is smaller than the sidebar and the sidebar will need to scroll. When this happens I calculate the height of the two and see if the discussion panel is smaller and make them the same height and add a class `no-affix` which makes the sidebar relative positioning so it won't stick to the top.

See merge request !2417

[ci skip]

Previously it was "user has already been taken", when really we were
saying the user has already been reported.

Autofill abuse message text with user url. Closes #2838

See merge request !2396

Add the version each feature was introduced in GitHub importer



See merge request !2457

[ci skip]

Added advanced SAML troubleshooting

/cc @dblessing @balameb

See merge request !2456

Prevent StateMachine warnings from outputting during a cron task

[ci skip]

Closes #5931

See merge request !2458

[ci skip]

Closes #5931