Improve project home page usability
I looked at project page and saw next problems with it:
* a lot of information but not separated on blocks - hard to understand
* unclear how to contribute to project
Instead of complete redesign I followed step-by-step changes.
### Step 1
First of all I separated Repository and Contribution blocks.
Contribution block should makes it easy for people to contribute. Even when we visit GitHub project page its not clear how to start. Our Contribution section should help with it. All repository stats and download button moved to Repository block.

### Step 2
Next step was to make top section less loaded. I moved clone panel to sidebar because it is very heavy element and rarely used. If you use web editor - you dont even use it. If you work via http/ssh you will copy remote only once. So my idea - it should be on home page but should not be in center of attention.

See merge request !610
Use the configured display name in e-mails from Devise mailer
By default, it is set to "GitLab", but a user may configure the display name to something else.
See merge request !613
Improve help line for restricted domain signups
The setting may be misconstrued as only allowing access from certain domains. Add help to clarify this applies to e-mail domains.
See merge request !612
Improve documentation of configuring external issue trackers
There was some confusion over the deprecated `:issues_tracker_id` field. Added documentation.
Closes#1514
See merge request !580
Added " How to maintain tight control over the number of active users..."
Added " How to maintain tight control over the number of active users on your GitLab installation" to documentation.
Please check that documentation is OK before accepting Merge. I took if from https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/gitlab.yml.example#L149
cc/ @sytse
See merge request !1792
Fix Error 500 when searching Wiki pages
If a Wiki page turns up a hit in the search results, an error will occur:
```
Completed 500 Internal Server Error in 836ms
NoMethodError - undefined method `slug' for "test.markdown":String:
app/helpers/wiki_helper.rb:10:in `namespace_project_wiki_path'
app/views/search/results/_wiki_blob.html.haml:4:in `_app_views_search_results__wiki_blob_html_haml___2752621660395393333_70299911622700'
actionview (4.1.9) lib/action_view/template.rb:145:in `block in render'
activesupport (4.1.9) lib/active_support/notifications.rb:161:in `instrument'
actionview (4.1.9) lib/action_view/template.rb:339:in `instrument'
actionview (4.1.9) lib/action_view/template.rb:143:in `render'
```
An unhandled String containing the name of the Wiki page would be provided to the URL path generator. This MR handles that case.
Closes#1547
See merge request !592
Unescape branch names in compare commit
The upgrade in GitLab v7.9 to Rails v4.1.9 caused all branch names in the compare commit mode to be escaped (e.g. `/` to `%2F`). The compare mode would not always work when comparing against branch names with a forward slash.
Opted to unescape the branch name rather than use a wildcard segment to prevent escaping slashes because it seems like a more sensible URL. The slashes in this case aren't really represented by a tree structure (e.g. /compare/one/two/branch..another/branch/here).
* Closes#1399
* Closes https://github.com/gitlabhq/gitlabhq/issues/9105
See merge request !582
Fix config template from parse errors
62aa05dd0c added comments that were not commented out. CI test builds do a `cp gitlab.yml.example gitlab.yml` and thus were failing.
See merge request !602
Add snippet visibilty as parameter to API doc, closes#1562
## Description
Snippet visibility level was added to API but was not to its documentation.
Related to following commit: 928fc94c3d
@axil Can you review?
See merge request !601