Amimate > Play and Rewind buttons do not revert to disabled state when activated

[Bruce Schubert]

When the Play button is invoked, the button toggles to a disabled state for an instant and then reverts back to enabled. The same behavior is observed for the Rewind button.

The Stop button enabled/disabled state works correctly, however, it is initially in an enabled state even though the animation is stopped.

[Bruce Schubert]

Time: Fixed animation control button states. Resolves #50. - Configured rewind, stop, and play actions to non-lazy initialization; also ignoring property change events that are not applicable.

→ <<cset fb3ac284dc7f>>

[Bruce Schubert]

Button states now convey current animation state.