Add getter for animateFirstView property of ViewAnimator

Tooling for xml properties is easier/better if we can properly reflect the
xml properties at the Java language API level as well. We had setters/getters
for the other properties of ViewAnimator, but only a setter for the
animateFirstView property.

Issue #6104327 Inconsistency between XML API and Java API for widgets - ViewAnimator

Change-Id: Iede7231fa433ce14f7a8299da4cedd4720370bc8