New feature: Create file from UI

Now you are able to create a new file in repository from your browser.
You are not allowed to create a file if file with same name already
exists in the repo.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Feature test for New file feature

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Move part of file creation logic into separate context

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Refactoring for EditTree and NewTree controllers and contexts

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Hide new file link if not branch HEAD

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'feature/create_file' of /home/git/repositories/gitlab/gitlabhq
Merge branch 'master' of github.com:gitlabhq/gitlabhq