Adding a compile to option to allow users to compile with serial port 1
and 2 defaults switched.

This is helpful if you fry a serial port.

Compile with `OPTIONS=SWAP_SERIAL_PORT_1_AND_2_DEFAULTS`.
Avoid unused variable warning for targets with no beeper.
Add MSP_SET_ADJUSTMENT_RANGE and MSP_ADJUSTMENT_RANGES commands.
Add basic MPU6000 auto detection code.  De-duplictate repeated code in
MPU6000.
Fix unit test compiler warnings on rc_controls_unittest
Update telemetry_hott_unittest.
Update battery_unittest.
Update unittest_flight_imu.