Get the db version

def namedb_get_version(con):
    """
    Get the db version
    """
    sql = 'SELECT version FROM db_version;'
    args = ()

    try:
        rowdata = namedb_query_execute(con, sql, args, abort=False)
        row = rowdata.fetchone()
        return row['version']
    except:
        # no version defined
        return '0.0.0.0'