BHV-13454: Added `start()`, `stop()`, and `pause()` methods, and a `paused` property

Also fixed a rounding issue in the keyframe generator, and added support for `transform` (proprietary prefix removal). Simplified some of the JS and converted it to plain CSS.

Enyo-DCO-1.1-Signed-off-by: Blake Stephens <blake.stephens@lge.com>