Version 0.12.30

+ db module:
  + terminal table has been extended to include configuration of terminals notifications.
+ terminal_config module:
  + implemented terminal notificatin config.
+ executor module:
  + due to recent fixes in concentrator firmware and related software,
    there is no more need to slow down printing process artificially.
+ gui module now utilizes terminals.Terminals.reset_mainloop instead of stop_mainloop.
  + Terminals.reset_mainloop method has been added to provide a way
    to restart mainloop with a new set of terminal devices.
+ interface and mainloop module:
  + mainloop now properly handles non-notifyable terminals.
  + refactored processor interfaces to support optional notifications.
+ tariff module:
  + 24:00 value in zero_time db attribute now represent undefined zero_time.
  + reworked DynamicTariff and DynamicTariffResult to correctly support
    zero_time option.