Make compatible with Due and add boards in boards.h

1. Make library compatible with Due except the examples
2. Add board definition in boards.h and do radio reset on every RedBearLab boards
I think in the V2.0 and later boards, the Arduino RESET line is also being routed to the nRF8001 so even if the radio reset command is not sent, the code will work. The the code above is a work around specific to the v1.1 and v2012_07 shield versions which did not map any Arduino pin to the nRF8001 RESET and only had a POR circuit.
Since the code here is only a work around I am very reluctant to add it for all redbearlab boards that do not have this problem. Please confirm my understanding.