Multiple fixed and finished the implementation of the SQLite backend.
Try to load the database before trying to attempt a rescan.
Delete the metadala list for backends that allocate them on demand.
Moved some generic functions to the databse class.
Renamed utils header to avoid rare QtCreator bug.
Moved the default database class to QListDB and disallow leaking CMAObjects outside this class.
Rewrote QListDB and CMAEvent to use the new internal API.
Moved the file format constants to the base database class.
Moved the metadata loading methods to the base database class.
