Add support for Adafruit Bluefruit LE SPI Friend

[jfpoilpret]

Refs:

• https://www.adafruit.com/product/2633
• https://github.com/adafruit/Adafruit_BluefruitLE_nRF51/tree/master

[jfpoilpret]

I will start to work on this issue on branch https://github.com/jfpoilpret/fast-arduino-lib/tree/AdaFruitBLEFriendSPI