HAL_PX4: fixed a scheduler bug that affects UART IO

we need to detect if we are in a timer task using a PID, not a
flag. This is the same type of bug I fixed last week, but now fixed
properly.

The bug could well be the "USB bug" that Craig has been chasing
AutoTune: bug fix and GCS messages
Copter: bug fix to convert old batt params to BATT_ lib
sensor hil fix
Copter: Correctly set limit.lower flags for Tricopters

Resolves #536
Copter: autotune set original gains on reset

Update from Leonard
Copter: autotune bug fix for starting autotune

log completion to dataflash
Copter: slow start motors from 0 to min throttle
Copter: pre-arm check speed is less than 50cm/s
Rover: added SKIP_GYRO_CAL option
Rover: bring MAVLink stream handling inline with plane
Rover: slow parameter send check to 5Hz

this solves an issue with current MP