Update Support library gradle build files. DO NOT MERGE.

Means we can now develop the support lib using
Android Studio and Gradle.

Need to update the Gradle prebuilts.

(cherry picked from commit 6a4c14b929df9d5ca592e0ee178bfd8784fe7c0a)

Change-Id: I90cebec4b492689f24a9669663630c0f02fd1035
8 files changed