python: Adjust to changes of GetChannelInfos()
Use GLib module instead of GObject for timeout_add and source_remove
Use keyword argument in constructor of Gtk.ActionGroup

Fixed deprecation warning https://wiki.gnome.org/action/show/Projects/PyGObject/InitializerDeprecations
Mark RecordingsDirectory property as construt
Use system's path to python binary in gnome-dvb-setup and gnome-dvb-control