Fixed Mudblood.Screen.Gtk.
Add key modifier support.
Mudblood.Screen.Vty: Quit on Ctrl-C.
Mudblood.Trigger: Added combinators 'gag' and 'keep'
Added Mudblood.Contrib.Logfile

This module provides a trigger that maintains a logfile.
Mudblood.Screen.Vty: Fix history.

Fix the case when a previous history entry was modified and entered
again.