Screen rotation support

SensorProvider class is designed to abstract sensor framework and
provide all sensor related notification for xwalk (currently support
rotation, orientation, may support motion, compass, geolocation
and gyroscope in future). TizenSystemSensor is the platform
depended part for Tizen mobile system. It is designed to not depend
Tizen in build time.

ScreenRotation class is an observer of SensorProvider to rotate the
graphic layer. It doesn't support web API in current stage.