devices: rename VideoDevice to Video

No functionality changes, only naming

Change-Id: I4f33a6862a071749512b2a8613451fe319ffbd13
Signed-off-by: Martin Polednik <mpolednik@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34391
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>