created entry to add in add activity
merged with chris's addEntry
UBudgetApp now a field in add entry activity
implemented the callback and the real add entry
made the entry add itself to the Budget object
fixed the bug where Budget wasn't initiating the list of entries
made Budget initiate its entries list in the constructor
deleted the EXTRA_MESSAGE that was not being used
got rid of a few TODOs, fixed the clear button to accept a View object as parameter, and added some missing comments.
Merge pull request #27 from coldstar96/addEntry

Still need to link the add budget view once that's ready.