more precise range conversion for SBus input signals
Non-destructive handling of failsafe signals, distinction between frame loss and signal loss.
This kind of handling might be moved upstream into the application, once alarms are propagated by the ORB system.

This change is compatible with RX failsafe settings, but does not rely on it (uses SBus flags instead).
First stab at implementing better RSSI based connection status estimation, still needs some work and testing
Improved S.Bus scaling based on scope measurements
Allow forceupdate in all conditions
Auto-update of IO firmware, shorter preflight check alarm
Further improved S.Bus scaling
Cranking up bus speeds for all sensors to achievable 10.4 MHz, will cut the bus lock time to half
Enabled MPU6K and updated startup script to start all sensors
Merge pull request #552 from PX4/spi_speedup

Cranking up bus speeds for all sensors to achievable 10.4 MHz
Added LOG_ MAVLink messages
Merge branch 'master' of github.com:PX4/Firmware
Re-introduced AQ MAVLink files since we have had them around before
Merge branch 'master' into vector_control2
multirotor_pos_control: default parameters updated