frontend: Support for Vm boot menu

Add checkbox to New/Edit VM dialog and RunOnce dialog allowing user to
specify whether menu should be shown on system boot.

Change-Id: Ic181909f9f3c0d68162029fb0584b6d5afc5af5d
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1047624
Signed-off-by: Martin Betak <mbetak@redhat.com>