Added some Assignments data for Testing.
Assignment titles shown in basic list view.
Added points and status to Assignments list items

-Assignment list items display points earned/points possible
-Assignment list items display their status (i.e. upcoming, current,
past due, closed)
-Centered the list view's empty text.
Moved padding from list view to list items.
Added more test data for Assignments.

The AI class has the most diverse data, covering all 4 possible
statuses.
Added empty and loading messages to AssignmentsFragment
Fixed R.id collision between empty views for Documents and Assignments

-Changed empty views to use custom IDs instead of android.R.id.empty
-Added more Assignments test data
Set the displayed fraction digits to a max of two for points
earned/possible.

-Added a NumberFormat to format assignment scores
-Added scores to some test data
Removed a Logger message.
Created package for Adapters.

-Moved DocumentsAdapter and Assignments adapter to adapters package
-Moved DocumentsFragment to fragments package
Created data model class for grades.
Added inital grades loading framework.

-Created Grade data model class
-Created GradesLoader to load data into the Fragment
-Created GradesDataSource interface
Removed placeholder TextView from the Grades layout.
Added empty and loading messages to the grades list view.
Hooked up GradesAdapter to the Grades list view.
Added a missing xml file from last commit.
Added Test Data for Grades
Added sections to Documents listview.  

-Added "Folders" and "Files" sections headers.
Hides Documents list separators when there are no items in the category.