Added SPI hal
Added driver for the max7221 7segment driver
Added test code for the 7segment driver
Added driver for the demultiplexer
Added test code for the LED multiplexer
Simplified setting SPCR to a single statement
Aliged expressions and correctly mark beginning/end
Merge branch '7seg'

Conflicts:
	SteeringNode/main.c
	drivers/CMakeLists.txt
Merge branch 'master' of github.com:UnicornRaceEngineering/g5-nodes