Change cancel/end behavior of animations to be synchronous

Previously, cancel() and end() calls would simply log a message to
be handled later by the animation handler. This caused problems with
coordinating complex animations, where some start() events for
future animations would occur before end() events for animations already
completed.
The change is to make these events synchronous (and require them to be
called from the appropriate thread), simplifying the code and the usage.

Also, fixed various timing and event bugs in AnimatorSet, and removed
the getter/setter properties from ObjectAnimator, since an earlier change
makes these properties undesirable (because the code will use a faster
JNI approach instead of reflection when it can).

Change-Id: I05c16645c2a31a92048a6031ddb126eb4312a946