HAL_PX4: rework Scheduler using hrt calls

thanks to Julian Oes for the suggestion
HAL_PX4: use fd IO instead of stdio

this allows for hal console output from within timers, which is very
handy for debugging
HAL_PX4: removed some files not needed any more
HAL_PX4: update simple example
Plane: switch PX4 to attitude HIL for now

a bit easier to debug
CPUInfo: added output for PX4FMU
HAL_PX4: implement peek() and available()

keep a 1 byte buffer
HAL_PX4: support reboot
HAL_PX4: added a storage driver

stores 'eeprom' to a sdcard file
HAL_PX4: use write() in panic()

this allows panic from the UARTDriver
HAL_PX4: use /dev/ttyS0 for uartA

this also changes txspace and available to use FIONWRITE and FIONREAD
HAL_Empty: fixed throttle in Empty RCInput
HAL_PX4: initial RCInput driver (overrides only)