Broadcast performance fix

fixes CAT-893:
The performance of broadcasts is improved now, Air Fight runs very smoothly again. Also the correct restarting of actions is guaranteed (I've added 2 regression tests for that).

Actions to restart are now precomputed per sprite and looked up during execution on the stage.

Jenkins testrun:
https://jenkins.catrob.at/view/All-Categories/view/Catroid-multi-job/job/Catroid-Multi-Job-Custom-Branch/1829/
It seems that there's a problem with the internet connection of the device. However, there's nothing changed in the web package in this PR.
What about `Collections.<String, List<String>>emptyMap()` (don't know if you need the type parameters)? It does not allocate a new map, even if the effect might be versy small. Same goes for the other occurrences below.