Support configurable attachment size in Application Settings page

### What does this MR do?

This MR provides the ability to configure the maximum size of an attachment inside a note. A parameter has been added to the Application Settings page.

### Are there points in the code the reviewer needs to double check?

What should be done with the legacy note attachment validation? I added code to make the validation work with the configurable setting. I could see an issue where an admin lowers the limit from 10 megabytes to 5 megabytes, which could cause an existing model to be invalid.

### Why was this MR needed?

We often have attachments that exceed 10 MB, and it would be nice to be able to override the defaults.

### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

See Issue #1258

### Screenshots

Before:

![Screen_Shot_2015-03-29_at_3.06.53_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/6013a1dbc8cf61a63e93744149937fa0/Screen_Shot_2015-03-29_at_3.06.53_PM.png)

After:

![Screen_Shot_2015-03-29_at_3.12.34_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/f3518af7e8653ba40f0a3579456da6ad/Screen_Shot_2015-03-29_at_3.12.34_PM.png)

See merge request !407

Import GitHub, Bitbucket or GitLab.com projects owned by authenticated user into current namespace.

Addresses #1347.

Untested since I'm in a bit of a hurry. Will definitely have time to test and add unit tests before the 7.10 release :)

See merge request !481

Archive repositories in background worker.

Depends on https://gitlab.com/gitlab-org/gitlab_git/merge_requests/17 being merged, a new `gitlab_git` being released and this MR's `Gemfile.lock` being updated..

See private issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2173.

To do after this is merged: Update https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-cookbooks/gitlab/templates/default/sv-sidekiq-run.erb in omnibus.

See merge request !436

Don't allow username to end in period.

The current behavior doesn't do username referencing and mentioning in sentences like "I discussed with with @douwe." since `douwe.` is matched as a username.

Addresses private issue https://dev.gitlab.org/gitlab/gitlabhq/issues/2174.

See merge request !438

Ability to skip some items in backup

https://dev.gitlab.org/gitlab/gitlabhq/issues/1936

Now it is possible to run

```
sudo gitlab-rake gitlab:backup:create SKIP=repositories,uploads
```

available options: repositories,uploads,db

See merge request !470

Check symlink mode as a String for file_type_icon_class

The file mode for a symlink just got changed in `gitlab_git`, see https://gitlab.com/gitlab-org/gitlab_git/commit/8ae14bb84b94a2ec15f8a639fb82f0f55c77ad69

See merge request !487

Fix bug where error messages from Dropzone would not be displayed on the issues page

Closes #1258

See https://gitlab.com/gitlab-org/gitlab_git/commit/8ae14bb84b94a2ec15f8a639fb82f0f55c77ad69

Conflicts:
	lib/gitlab/markdown.rb

Unbind task item checkbox events and then rebind them

Fixes #1340

This issue was caused by this line: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/views/projects/issues/update.js.haml#L17

`new Issue()` gets called on every JS-based issue update, and all the binds in the constructor get re-applied without first unbinding the existing ones. Right now my fix is *only* for the checkbox events, and I suspect there are similar issues still present for other events.

See merge request !478

Don't use chmod_R for backup tars

When creating backup tar files, only change permissions on the `db`, `uploads`, and `repositories` directories, not their contents.  See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/1716#note_40472

See merge request !1744

Don't leak private group existence by redirecting from namespace controller to group controller.

See merge request !440

Fix admin user projects lists.

The admin user personal projects lists wasn't being rendered anymore.

cc @marin

See merge request !442

Better looking milestone lists

### Before

![milestone-before](https://gitlab.com/gitlab-org/gitlab-ce/uploads/1366ade74d76b067fdc8707d31d2bffc/milestone-before.png)

### After

![milestone-after](https://gitlab.com/gitlab-org/gitlab-ce/uploads/80ae1c1f77eae5dff8ee61c4271bec17/milestone-after.png)

See merge request !484

Fixes #1340

Allow ability to delete branches with '/` in name

Fixed issue where only 25 commits would load in file listings

Fixes #1310

See https://gitlab.com/gitlab-org/gitlab-ce/tree/master and it will only show the first 25 files commit messages.

See merge request !477

Update documentation on issue closing pattern.

See merge request !475

Added badge to commits tab

Fixes #1261

See merge request !465