Link cross-project cross-reference notes to correct project.

- Fixes #1431: Don't crash when an MR from a fork has a cross-reference comment from the target project on of its commits.
- Include commit comments in MR from a forked project.

To accomplish this, the Commit model needs to know about its project. Adding this attribute also simplifies a bunch of other methods that deal with a note's target, that previously had to have special logic for when it belonged to a commit.

See merge request !554

Tweak issue page a bit 

Add project activity atom feed and show atom feed buttons everywhere where applicable.

See merge request !555

Change "Sam" to "Dmitriy" in feature steps

"Sam" was too short and generic and caused invalid test failures due to finding other people with names like "Sammie" or "Samuel" unexpectedly.

See https://ci.gitlab.com/projects/1/builds/35205 and https://ci.gitlab.com/projects/1/builds/35093 as two recent examples.

See merge request !571

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This crappy test framework stuff fails randomly. So I can't reliably
run it on my local machine.

* Include creation time
* Include author without avatar
* Move assignee to the right
* Include comments counter by default, gray it out when there are 0
  comments.

* Include creation time
* Include author without avatar
* Move assignee to the right
* Remove action buttons. IMO they are useless and a bit annoying
* Include comments counter by default, gray it out when there are 0
  comments.

"Sam" was too short and generic and caused invalid test failures due to
finding other people with names like "Sammie" or "Samuel" unexpectedly.

Update d3_rails and jquery-atwho-rails

We were a bit behind on these JS libs, so this updates them.

AtWho made a few API changes for which I had to update our usage.

Should fix #1457 as well.

See merge request !542

Update mentionable shared examples to be (a bit) more understandable

These shared examples were super confusing, and honestly still kind of are, but they should be a bit better now.

I encountered a bunch of headaches in these examples while refactoring ReferenceExtractor, so that's how I ended up changing it.

See merge request !1780

Add default_url_options initializer

Fixes #2266

See merge request !1791

Use fixed width icons in all nav sidebars

| Before (watch the Network and Graphs icons as the sidebar collapses): | After: |
| :--------: | :------: |
|![Screen_Recording_2015-04-23_at_02.31_PM.mov](https://gitlab.com/gitlab-org/gitlab-ce/uploads/338aa382ff7609978cd900db29379f3f/Screen_Recording_2015-04-23_at_02.31_PM.mov.gif)|![Screen_Recording_2015-04-23_at_02.30_PM.mov](https://gitlab.com/gitlab-org/gitlab-ce/uploads/24af635f253688690b42da60271e7afb/Screen_Recording_2015-04-23_at_02.30_PM.mov.gif)|

Uses the `icon` helper, because I can't help myself!

See merge request !566

Fixes #2266

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>