libweston: add weston_output::color_profile

Add API to set an output's color profile. This new function can also be
called while the output is enabled. This allows changing the output
color profile even at runtime if desired.

color-noop has no way of creating weston_color_profile objects, so it
just asserts that no color profile is set.

color-lcms does not yet implement taking the output color profile into
account, so for now it just fails everything if a profile is set.

weston_surface_color_transform_fini() was previously used only prior to
freeing the struct, but now it is used also to just clear the struct,
hence it needs to reset the fields.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>