small fix
songdb.DB.iteritems
cleanup
songdb: simple Cache class implementation
songdb: use Cache
songdb.iterSongs()
fixes
small fix
security check
small fix
small fix
utils: ReadWriteLock implementation
songdb: use ReadWriteLock

This should fix any sqlite3 error like:
   OperationalError: database is locked

This error happens when some reading-cursor and we try to write.
fixes