Decouple sensor alignment from all acc/gyro/mag drivers.

This resulted in the removal of duplicate logic, duplicate code and the
removal of a temporary buffer per-driver.

The NAZE specific sensor alignment is now contained within the core code
instead of in the drivers.
The sensor alignment is determines by the sensor initialisation code.
The alignment of sensor readings is now performed once and only by the
appropriate sensor code, see usages of alignSensors().

The acc/gyro/compass driver code is now more reusable since it has no
dependencies on the main code.