fix. default start timestamp must precede default end timestamp
mod. bytes_added_rev_user_query to more generic rev_user_query and inclusion of connection logic
mod. bytes_added_rev_len_query to more general rev_len_query.  Included connection objects.
add. exception type UMQueryCallError to flag exceptional cases
fix. call to 'cursor.fetchone' for MySQLdb obj
mod. bytes_added_rev_query to rev_query.  Added connection refs.
mod. decoupled MySQLdb dependencies in metrics code.
mod. query_method_deco decorator on live_account_query.  Removed MySQLdb connection dependencies in live_account
mod. refactor query_calls, more generalized, include connector refs.