Update permissions for issue tracker management

Don't allow guest or reporter to set assignee, milestone and label when create or update new issue and merge request.
After this change `Guest` and `Reporter` rule is used to report issues but only `Developer` and higher roles can manage issues (schedule milestone, assign to user or close any issue)

Also I removed some duplication code between issues and merge requests and put all issuable partials in one directory

See merge request !890

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

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

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

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

added info about GitHub importing

Added info that importing doc also works for GitHub EE.

https://dev.gitlab.org/gitlab/gitlabhq/issues/2410#note_49396

See merge request !1878

Add SAML to list of social_provider

Resolves issue 1888.  Still an issue because the SAML link under Connected Accounts will not have a logo.

See merge request !891

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

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

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

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

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

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

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

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

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

Have sidebar labels disappear behind content instead of hide immediately when collapsing.

I'm not sure how to make a gif out of it, but I promise it looks pretty :)

See merge request !888

prettier highlighting of active link in the sidebar

Before:

![Screenshot_2015-06-25_11.17.08](https://dev.gitlab.org/gitlab/gitlabhq/uploads/851606a122c1d1174d0f97857ad472d3/Screenshot_2015-06-25_11.17.08.png)

After:

![Screenshot_2015-06-25_11.17.42](https://dev.gitlab.org/gitlab/gitlabhq/uploads/b8dc55bcd76dac29652ef5d25f99ccff/Screenshot_2015-06-25_11.17.42.png)

Only with this theme it's not an improvement (this is an honest merge request (trademark pending)) :

![Screenshot_2015-06-25_11.18.35](https://dev.gitlab.org/gitlab/gitlabhq/uploads/5d631a11ee866f5fc51e985b02a836ba/Screenshot_2015-06-25_11.18.35.png)

See merge request !1879

Show a random Markdown tip in the textarea placeholder

cc @darby

See merge request !879

Removed the icons from the New Issue and New Project buttons

Fixes #1869

No more icons!

See merge request !885

Change the default admin password

Closes internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2422

See merge request !865

Performance improvements

* store @participants in variable
* store result of subscribed? call into variable

In total it reduce amount of SQL queries for issue or merge_request with 10 comments/participants almost twice.

See merge request !883

Add 2FA status to user admin API

This MR adds the `two_factor_enabled` field to the admin's API to indicate whether a given user has enabled 2FA.

See merge request !881

Updated merge request merged web hook to correctly fire action=merged.

I believe this merge request will fix both issues #879 and #498.

If a merge request was merged via the command line, the correct web hook was fired with the field `object_attributes.action = "merge"`. However, if the merge request was merged via the web UI, the webhook would be fired with `object_attributes.action = "open"`.

See merge request !780

Fixes #879
Fixes #498