HAL_PX4: fixed auto-flow control

the 6 bytes written to break the radio out of bootloader broke
auto flowcontrol detection
Plane: set version to 3.0.4beta
Frame_params: Added Iris with Front Mount Go Pro
GPS: correct NAVFILTER parameter description

These corrected values match the GPS_Engine_Setting enum in GPS.h
Thanks to Adolfo R for noticing the issue and providing the fix
APM_OBC: adjusted docs for FS_HB_PIN

thanks to Warren for the question
AP_Common: moved map_baudrate() into AP_Common

this version supports a much wider range of baudrates
GCS_MAVLink: moved main update() routine into GCS_Common.cpp

this fixes a common timeout error with loading large missions, and
means less per-vehicle code
Plane: changed baudrate parameters to 16 bit
Plane: update baud rate parameter descriptions
Plane: updates for new GCS_MAVLink API
Copter: change baudrates parameters to 16 bit
Copter: update baud rate parameter descriptions
Copter: updates for new GCS_MAVLink API
Rover: change baudrates to 16 bit

allows for much higher serial baud rates
Rover: update baud rate parameter descriptions
Rover: updates for new GCS_MAVLink API
AntennaTracker: updates for new GCS_MAVLink API