Refactorings Done

• The God Class smell pointed out that ExpenseItemActivity had a bunch of Bitmap-related code that could be extracted. I used the refactoring and it took the code out into a new class, which I named DrawableBitmapConverter. (Adam)
• The God Class smell pointed out that we have redundant alert dialog code in many places where we're performing validation. The suggested refactoring didn't quite work how I wanted it to, so I did the refactoring manually, using a new class called ValidationErrorAlertDialog. I also took the opportunity to move the validation code into the model. (Adam)

Check out this pull request for the above changes.