add_cycle_complete_receiver not supported for included animations

it seems only animations derived from ColorCycle currently support the callback used by sequence when they complete. I added this code
`def onComplete(sequence):
print("completed sequence", animations.current_animation, sequence)

animations.add_cycle_complete_receiver(onComplete)
`
to the all-animations example, and it is invoked only when the CustomColorChase ends its cycle. outputting:
"completed sequence "

Start with the all-animations example and inspect how add_cycle_complete_receiver is handled for ColorCycle and CustomColorChase. Trace the completion callback through the animation sequence entry points, then verify that the callback runs when included animations complete their cycles, not only ColorCycle-derived animations.

Scritto dal modello di indicizzazione a partire dal testo della issue.