Initial commits - MythTrack Content Provider classes

MythTrackDatabase contains methods for creating, reading, updating, and removing data from the hero and item tables. It contains a subclass that manages the creation and updating of entire tables in the SQLite 3 database.
MythTrackContract is a contract class that defines table and column names, content provider URIs, common projections and selection, and enumeration values for the database.
MythTrackBackup implements the Google Backup API to save and restore the database file.