actor: Add delay to the easing state

actor: Add delay to the easing state

It should be possible to set up the delay of a transition, but since
we start the Transition instance before returning control to the caller,
we cannot use clutter_actor_get_transition() to do it without something
extra-awkward, like:

  transition = clutter_actor_get_transition (actor, "width");
  clutter_timeline_stop (transition);
  clutter_timeline_set_delay (transition, 1000);
  clutter_timeline_start (transition);

for each property involved. It's much easier to add a delay to the
easing state of an actor.