OK animation and sound support is added. I haven't made the above changes to CmpVisualActor yet, pending discussion, that leaves a few animation bugs.
I found another case that needs a different solution anyway: if units are right on the edge of the gate's range, they might walk in and out of range quickly, causing the animations to start and stop abruptly which looks ugly. In this case, it would be useful to "reverse" the direction of the animation instead of starting a new one.
Related issue: Pureon mentioned it would be helpful for ship sails to have finer control of animations (particularly direction and speed). The whole system has other shortcomings, so it needs further discussion.
