Hardware abstraction should make for easier test harnessing in the future.
Conflicts: firmware/common/hackrf_core.c firmware/common/hackrf_core.h
Conflicts: firmware/CMakeLists.txt firmware/hackrf_usb/Makefile firmware/mixertx/Makefile firmware/sgpio/CMakeLists.txt firmware/simpletx/Makefile firmware/spiflash/CMakeLists.txt firmware/startup/Makefile firmware/startup_systick/Makefile firmware/startup_systick_perfo/Makefile