frontend: ctrl-alt-delete changes

changes in this patch:
 - removed "pass c-a-d to vm" from console options as this option
   doesn't behave well on windows > xp
 - added a function "remap c-a-d to control-alt-end" for spice and vnc

Change-Id: I0ef2c0a2c071cafa13ec90a10635ea61b78344a1
Signed-off-by: Frantisek Kobzik <fkobzik@redhat.com>
Bug-Url: https://bugzilla.redhat.com/1029441