General sensors

Working on a general interface for sensors

https://groups.google.com/forum/#!topic/phoenixpilot/d0NHq1YGrCs

This creates queues for all of the sensor classes (baro, mag, gyros, accels) and a general interface for registering them and gaining access to them.  So far what is ported is 
- MPU6000
- HMC5883
- MS5611 will be easily with https://github.com/PhoenixPilot/PhoenixPilot/pull/160

The drivers for FlyingF3 and FlyingF4 need bring up to date.