Redesign the StatusIcon Service.

[timlau]

The current dk.yumex.StatusIcon is too complex and error prone and it need to be redesigned.

• Remove the Gtk.StatusIcon UI, it is depecated (3.14)[1] and will be removed from a future version of Gtk
• Rename the service to dk.yumex.UpdateChecker.
• Remove all the handshake between yumex-dnf client and the service.

  The new version shall perform the following actions.

• [x] Check for updates on a user defined interval.
• [x] Show a Notification when new updates is found and lauch yumex-dnf on users request.
• [x] Give the user an option to mute the Notification, So the user don't receive more Notification about updates until next day.

[1] : https://developer.gnome.org/gtk3/stable/GtkStatusIcon.html

[timlau]

Done