sensorservice: Add legacy sensors fusion.

This change allows devices with accelerometer & magnetometer but
without gyroscope to still get virtual sensors such as Gravity,
Linear Acceleration, Orientation & Rotation Vector.

Can be disabled with BOARD_USE_LEGACY_SENSORS_FUSION := false

Change-Id: Ibb90b70845c766ab52c843557446e34649a7d6d9
SensorEventQueue: Allow setRate on sensor enable

4.3 and earlier would set the sensor rate on activation and then set it again
when setRate was called.

Some sensor HALs assume this will happen and ignore the first setRate

Conditionally the first one back in for such broken HALs

Change-Id: If1c259b0fd5517a1272cdad0a1abf1fe0fb5a7d1