Add ability to toggle looping animation or stop at the end.

[dgarciabriseno]

Currently animation loops forever, it may be good to have an option for it to stop when the last time is reached.

The logic for frame animation is done here in TickFrame https://github.com/dgarciabriseno/helios/blob/d53fcf6584aa4f80e9d468e37ce4e4f0d515e502/UI/animation_controls.js#L161-L183

Rather than continuing to animate forever, there should be some flag which when set, will make _GetNextFrame execute Pause() instead of just rolling over back to the start time.