Directory

# new feature : sublime-style collection/resource tree editor

I like the way sublime-text allows to browse resources directly in the editor, so thought about cloning this feature. This is a rapid first go. 

The pull request splits the outline editor into two : the classical ```outline``` + a new area for browsing database collections and resources called ```directory```:

![exide-directory](https://cloud.githubusercontent.com/assets/1168053/4225452/d055ddaa-392d-11e4-9704-1f4c14c75203.png)

It is pretty straightforward to use it: click on collections to open/close them, click on resources to open them in the editor. 

Some thought for future development: 
- add drag and drop + rename features 
- find good way to display/modify resources permissions
- keep tree state for later sessions (and also when re-opening a collection)

Also added in the pull, some small fix to make the git features work again with version 2.1.0.

Cheers,
Christophe