Copter: bugfix for starting in LOITER

Loiter's Roll-Pitch mode was not being set on start-up.
Copter: BugFix DO_SET_ROI returns Lat,Lon,Alt to GCS
TradHeli: Fix for yaw offset switching.  Yaw Offset should switch on and off with the main motor, not waiting until the rotor has reached full speed.
HAL_PX4: fixed build for new PX4Firmware
AP_HAL: support uartD on some boards

PX4 and SITL get an extra UART
HAL_AVR: added NULL uartD
HAL_SITL: added uartD
HAL_EMPTY: added uartD
HAL_FLYMAPLE: added uartD
HAL_LINUX: added uartD
HAL_PX4: added uartD
GCS_MAVLink: added support for 3 UARTs

support 3 UARTs on non-AVR platforms
Copter: added uartD support

this also brings GCS_Mavlink.pde closer to the plane implementation
Copter: removed extra features of copter telemetry merge
Copter: added SERIAL2_BAUD and rename SERIAL3_BAUD to SERIAL1_BAUD
PX4: enable uartD by default in rc.APM
TradHeli: disable AutoTune for Tradheli compile

We need the flash space, and this probably won't work for tradheli anyway since tradheli needs most of the control from Feedforward rather than P term.  And D-term is very very bad.
TradHeli: enable Landing Collective when we are not moving

This prevents full negative pitch when touching down in Alt Hold or Auto-Landing.
TradHeli: rename Stab_Col parameters

With H_ prefix they appear with the rest of the tradheli specific params in the parameter list.
TradHeli: Minor change to two param defaults

Also one param name in the code clarified.