Bump underscore-rails to ~> 1.8.0

Addresses #2857

See merge request !2193

fixes the search for projects

Also makes improvements for jQuery queries. <br/>
@creamzy @skyruler <br/>
Fixes issues introduced in MR for #3943

See merge request !2194

Fix spelling of "it's" to "its" where appropriate.

[ci skip]

See merge request !2196

Fix Error 500 when doing a search in dashboard before visiting any project

If a search turned up an issue, under certain conditions you would see this error:

```
ActionView::Template::Error (undefined method `path_with_namespace' for nil:NilClass):
     6:   - if issue.description.present?
     7:     .description.term
     8:       = preserve do
     9:         = search_md_sanitize(markdown(issue.description))
    10:   %span.light
    11:     #{issue.project.name_with_namespace}
    12:   - if issue.closed?
  lib/gitlab/markdown/upload_link_filter.rb:36:in `build_url'
  lib/gitlab/markdown/upload_link_filter.rb:31:in `process_link_attr'
  lib/gitlab/markdown/upload_link_filter.rb:18:in `block in call'
  lib/gitlab/markdown/upload_link_filter.rb:17:in `call'
  lib/gitlab/markdown.rb:127:in `gfm'
  lib/gitlab/markdown.rb:24:in `render'
  app/helpers/gitlab_markdown_helper.rb:61:in `markdown'
  app/views/search/results/_issue.html.haml:9:in `block in _app_views_search_results__issue_html_haml__4127460390996300432_59973760'
  app/views/search/results/_issue.html.haml:8:in `_app_views_search_results__issue_html_haml__4127460390996300432_59973760'
  app/views/search/_results.html.haml:20:in `_app_views_search__results_html_haml__589475855773452465_61761440'
  app/views/search/show.html.haml:5:in `_app_views_search_show_html_haml___1852335078065998536_69780120'
```

Confirmed this is issue still happens in GitLab 8.4, and it also happens on GitLab.com. Here's how to reproduce:

1. Login in a new browser.
2. Enter a search term on the top right that will land a hit in the "Issues" (e.g. GitLab).
3. Click on "Issues" tab. You should get an Error 500.

The issue is that @project isn't assigned to anything.

See merge request !2110

Make migrations reversible

See merge request !2191

Addresses #2857

New project button with filter in header.

Fixes #3943 
![Screen_Shot_2015-12-21_at_3.47.01_PM](/uploads/f7f952440b4bb4b55f62241bbc328c95/Screen_Shot_2015-12-21_at_3.47.01_PM.png)


See merge request !2165

Button height

old
![Screenshot_2015-12-23_15.48.12](/uploads/0e6c5696262475c197f8fcbf00199132/Screenshot_2015-12-23_15.48.12.png)

new
![Screenshot_2015-12-23_15.48.45](/uploads/1d6bdf96f7c90b65f4a6b21df3951370/Screenshot_2015-12-23_15.48.45.png)

also including MR page

See merge request !2188

Add project permissions to all project API endpoints

This standardizes all the project API formats. Also needed to support Huboard.

See merge request !2090

border bottom for last comment fixes double line issue

Since image uploading isn't working atm. Will upload screenshots when it works again. 
https://unsee.cc/mosapine/
Fixes #3955 

See merge request !2175

New buttons

OLD
![Screenshot_2015-12-22_21.42.59](/uploads/79e85727586f7b917b8ab9ef867e79dc/Screenshot_2015-12-22_21.42.59.png)

NEW
![Screenshot_2015-12-22_21.42.21](/uploads/aee54160f17e0502e14ca5c754dcfe50/Screenshot_2015-12-22_21.42.21.png)


See merge request !2179

Fix method that ensures authentication token

Until now, `ensure_#{token_filed_name}!` method didn't persist new token in database.

This closes #4235.

See merge request !2185

Bump jquery-rails to ~> 4.0.0, jquery-ui-rails to ~> 5.0.0

Closes #2859 

See merge request !2183

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

Link to the gitlab-ci.yml file of GitLab itself.

I'm hunting for this link from time to time in customer demo's so I think it is useful to add.

/cc @ayufan 

See merge request !1993

Bump sass-rails to ~> 5.0.0

Addressing gitlab-org/gitlab-ce#2857

See merge request !2184

Improve emoji picker

This request uses an emoji image sprite to show big set of emojis. The sprite has been made based one gemojione gem images. The categories are retrieved from https://github.com/jonathanwiesel/gemojione/blob/master/config/index.json as well.

Some categories are pretty poor, it can be extended in the future.

It's a first step on the way to improve picker.

The first implementation was using https://github.com/iamcal/emoji-data project, but there was huge incompatibility with gemojione emojis set and I had to drop that solution.

![Screenshot_2015-12-22_23.26.27](/uploads/7d323eb0586204ac92915b41233b97ec/Screenshot_2015-12-22_23.26.27.png)


See merge request !2172

`runners_registration_token` now creates a new token if it is blank.

Make CI Lint form synchronous

This removes `remote: true` from CI Lint form, making it synchronous
form. This also removes some complexity related to displaying lint
messages.

View also has been updated, removed deprecated Bootstrap 2 tags.
Improved design.

See merge request !2171

Until now, `ensure_#{token_filed_name}` method didn't persist new token in database.

This closes #4235.