ItmsContentProvider, QuestionFragment: Simplify.

Remove the unncessary intermediate Classifications table.
QuestionFragment: Add some null checks.
ItemsContentProvider: Add code to POST the classification to the server.

Along with a method call to start the uploading, just to excercise it for now.
This is not complete and it is not yet using the zooniverse server's URI.
ListFragment: Add an Upload button to test the POSTing code.