wayland: implement resizing and maximization for wayland clients

To properly resize clients, we need to send them configure events
with the size we computed from the constraint system, and
then check if the new size they ask is compatible with
our expectation.

Note that this does not handle interactive resizing yet, it
merely makes the API calls work for wayland clients.

https://bugzilla.gnome.org/show_bug.cgi?id=707401
MetaWaylandSurface: cache the surface type until the first commit

Once the sizing is properly wired up, we need to make sure that
the size at the initial map is correct, and not always 0, 0 because
the buffer is not yet converted into a CoglTexture by MetaShapedTexture,
otherwise we end up sending out configure events at 1 x 1.
To do so, we cache the surface type in the initial state until the
first commit.

https://bugzilla.gnome.org/show_bug.cgi?id=707401
wayland: implement transient hints for wayland clients

wl_shell supports a set_transient() map request that is equivalent
to setting WM_TRANSIENT_FOR in X11, so implement that.

https://bugzilla.gnome.org/show_bug.cgi?id=707401