Add 'Property' object

This change adds a generic Property facility to the SDK, which allows an
easy way to reference fields (private or otherwise) in a general way.
For example, animations can use this facility to animate 'properties'
on target objects in a way that is more code- and compiler-friendly than
the existing String-based approach (for objects which have implemented
Properties, of course). The animator classes have been updated to use
this new approach (in addition to Strings, which are still more generally
useful for objects which have get/set functions but not Property objects).

The change also includes new Property objects on View (which can now be
used in creating animations on Views).

There is an unrelated change on GLES20RecordingCanvas to change the way we
cache bitmaps, which avoids spurious garbage by using an ArrayList instead of
a HashSet.

Change-Id: I167b43a3fca20e7695b1a23ca81274367539acda