Support editing target branch of merge request

### What does this MR do?

This MR makes it possible to edit the target branch of a merge request and adds a system note when this happens.

### Why was this MR needed?

Because lots of people requested this feature. :)

### Screenshots

**Edit MR page**

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/9b3d405bf7b5f945e35bae3534c2b67b/image.png)

**New MR page**

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/3657a2a9efad6d10e8470637d1166bdb/image.png)

**System note**

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/cc8066f3d3bdf09c0cce27193210567d/image.png)

### What are the relevant issue numbers?

* Closes https://github.com/gitlabhq/gitlabhq/issues/7105
* See: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/130!

See merge request !738

Add option to disallow users from registering any application to use GitLab as an OAuth provider

Addresses internal issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2264.

![Screen_Shot_2015-05-29_at_13.30.11](https://gitlab.com/gitlab-org/gitlab-ce/uploads/300f8e9ecbeb3d353ebc33a63cdef4e9/Screen_Shot_2015-05-29_at_13.30.11.png)

See merge request !742

User should be able to leave group. If not - show him proper message
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !743

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>

Shorten merge request WIP text.

![Screen_Shot_2015-05-29_at_11.37.46](https://gitlab.com/gitlab-org/gitlab-ce/uploads/5853d9057103bdaacded17798378f68e/Screen_Shot_2015-05-29_at_11.37.46.png)
![Screen_Shot_2015-05-29_at_11.37.49](https://gitlab.com/gitlab-org/gitlab-ce/uploads/be96ee32ab5a8f23835dc37306259b17/Screen_Shot_2015-05-29_at_11.37.49.png)

See merge request !741

Closes https://github.com/gitlabhq/gitlabhq/issues/7105
See: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/130

Add SAML support via Omniauth

Split of !669, with doc

See merge request !722

Include location.search and location.hash in URL for replaceState

Forgot these 😊

See merge request !740

Add Teaspoon for Javascript testing

Looking to expand our Javascript unit tests, and this gem makes things a bit better in that respect.

See https://github.com/modeset/teaspoon

See merge request !715

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

Improve MergeRequest tab-persisting behavior

Now uses the path instead of the hash.

See discussion in !728

See merge request !737

Allow special characters in users bio

Now uses the path instead of the hash.

See discussion in #728.

/:namespace_id/:project_id/merge_requests/:id/commits(.:format)

Remove extra brace

Extraneous curly brace creeped in prior commit.

See merge request !734

Make user settings account page nicer

* make 2 factor auth section `panel-default`
* make oauth buttons smaller
* remove primary button from reset token form

![Screenshot_2015-05-28_20.37.30](https://gitlab.com/gitlab-org/gitlab-ce/uploads/e536723e087b72a5c08b29072fb4972f/Screenshot_2015-05-28_20.37.30.png)

See merge request !733

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

Use panels instead of well for widgets in project sidebar

Cleaner look and less distractive

![Screenshot_2015-05-28_17.31.27](https://gitlab.com/gitlab-org/gitlab-ce/uploads/d4f8e58f76c7f62c488dd571c313e21e/Screenshot_2015-05-28_17.31.27.png)

See merge request !732

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

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

Conflicts:
	app/views/profiles/accounts/show.html.haml

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