modified .gitignore to ignore .vrx and .hex files
VRBRAIN: enabled the compilation of module bl_update for bootloader update from nuttx
VRBRAIN: added automatic update of bootloader from SD at startup
VRBRAIN: some not important adjustments
VRBRAIN: renamed external and on board drivers for MPU6000 and HMC5883 sensors
VRBRAIN: added filter dfu
AP_HAL_VRRBAIN: added comment
VRBRAIN: deactivated error on HMC5883 start
VRBRAIN: included module esc_calib for ESC's calibration from shell
VRBRAIN: deleted unnecessary customizations
VRBRAIN: changed the management of the pwm output
VRBRAIN: change default pin for analog input.
AP_Scheduler: added current_task static

will be used to debug stuck tasks on PX4
HAL_PX4: print overtime message on stuck task

this should make it easier to narrow down stuck task bugs
GPS: Include 75-class CPUs in RTK support since they will have 64 bit floating point values.
GPS: Fix dataflash logging bug in SBP driver
AP_HAL_VRBRAIN: removed empty lines
PX4: disable PX4IO RC handling in a clean way

Upstream PX4 Firmware provides a clean way to disable PX4IO handling by supplying the argument "norc" to "px4io start". After applying this fix to the rc.APM startup script, the quick hack contained in commit 180cceee of diydrones/PX4Firmware can be safely reverted.
PX4: added conversion lib for rotation
PX4: try to startup FMUv3 with right rotations