Plane: fixed a bug with setting stream rates 

this is what caused the "no sensors" problem in the 2.69 release
Plane: default the stream rates to 1Hz
HAL_PX4: changed scheduler priorities

put sensor priority above main sketch, to prevent occasional blocking
for sensor data
AP_GPS: removed unused AP_GPS_Shim.h
AP_GPS: ensure constructors zero all key variables

this prevents a crash on PX4 if a GPS is attached after startup
Plane: reset AHRS trim after a level operation
Rover: reset AHRS trim after levelling
HAL_PX4: show a message if we fail to upgrade PX4IO firmware
HAL_PX4: fixed a buffer handling bug

BUF_SPACE() was badly buggy, which could lead to memory corruption
Plane: prepare for 2.70 release
Plane: ignore control mode changes when in throttle failsafe

this prevents the receiver causing a temporary mode change
Git: Adding MacOS gitignore .DS_Store
Merge pull request #96 from jason4short/master

Please add this GitIgnore
build: split up the build system to allow for better board support

this will make it easier to support boards like the VRBrain
build: fixed eclipse build on Windows for PX4
Rover: change PX4 main baud rate back to 115200

we now use USB console
Copter: change PX4 main baud rate back to 115200
    
we now use USB console
Rover: removed obsolete files
Rover: default magnetometer to enabled

will be disabled by auto-detect code if not attached
Rover: don't override declination on startup