Added sections to Documents listview.  

-Added "Folders" and "Files" sections headers.
Hides Documents list separators when there are no items in the category.
Merge branch 'master' of https://github.com/dattorz/CascadeLMS-Android.git
Added ability to recieve and distinguish clicks on Files/Folders.
Added the ability to download Documents.

-Pressing a file in the documents list view will now download the file
it links to.
-Added INTERNET and WRITE_EXTERNAL_STORAGE permissions required for this
to the manifest.
-For testing purposes, Documents in FakeDataSource point to the same
image from the www.cascade.org website.