Fixed #17 by using a newly added cancel-method on the animator instead of the finish-method.
Added reset-method to the AnimationProducer Interface just for the logic of it.
Commented out all code in the various classes handling the manual addition of nodes at specific positions between their siblings. Have to properly redo this feature soon.
Thanks @Sanjo for making the names of the animation-classes shorter (#10, 8afbc9157c1efe931e20cbaa56bec28f7f0b8631) and giving Interface and abstract class more appropriate names.