[build] Port build system to Gradle
Merge branch 'master' into reconcile-master

Conflicts:
	sample/res/layout/activity_main.xml
	sample/res/layout/activity_sample_basic.xml
	sample/res/layout/list_item.xml
	sample/res/layout/list_item_basic.xml
	sample/src/main/res/layout/activity_main.xml
	sample/src/main/res/layout/list_item.xml