Remove Clutter and Cogl

Clutter and Cogl are not used by anything in oe-core, and in Gnome are
legacy components so are only used by a few applications.  The recipes
have already been moved to meta-gnome so they can now be removed from
oe-core.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>