Automated response: Stray tables could cause installer errors

Stray tables in an old Composr install could carry over to a new Composr install. Since these stray tables are not in db_meta, table_exists may return false even if the table exists. And when the addon / hook tries to create the table, an error occurs. This fix implements table erasing in the install. When overwriting an existing Composr install, the installer will delete every table indicated in db_meta to reduce stray tables existing.