add nrf24l01 library

files individually saved from http://www.tinkerer.eu/AVRLib/nRF24L01
add spi lib

add from http://www.tinkerer.eu/AVRLib/SPI
fix indentation
add more gcc flags

I prefer more pedantic compiler settings.
fix (minor) compile warnings
extend spi with spi_read_data
add registers for the plus version of the radio module
mirf wip
switch mcu to atmega328
fix makefile

- reduce spi speed because of missing crystal
- add fuses for atmega328
add tests for some components

add endless loop for testing
- serial
- pwm
- radio nrf24l01+
ignore built files
add gerber files for ordered pcbs

ordered 10 pcbs from seeedstudio