Second generation accommodations

* Removed RF22_SS define and now using the one defined in the SPI
library (SPI_SS_PIN).
* Modified SecondGenMake file (fuses, comments, etc.)
* Removed SS pin initialization in MAX6954 library in favour of the one
in the SPI library
* Removed the SS pin macro for MAX6954 in favour of the one defined in
SPI (SPI_SS2_PIN)
* Added SPI_SS2_PIN initialization in spi.c
* Modified the SPI pins for the atmega644 pin