Make behavior of ABSOLUTE pivot values more intuitive

Currently, you must call initialize() on RotateAnimation or
ScaleAnimation prior to calling start(). The reason is that the
actual pivot point used in calculating the transform is not set
until that method is called. This makes sense in the typical case
where the animation is running on a View and is using values relative
to the size of the View or of its parent. But if the caller sets the
values to be ABSOLUTE types instead, the sizes of the view and the parent
are irrelevant and the call to initialize() should not be needed (and
is not intuitive).

This fix automatically sets the internal pivot values in the case where
the value types are ABSOLUTE.

Change-Id: I74a0e462486efae08aa76e72c0d19d82f2a2677e