stm32l1 - added a dummy app for BlueNRG
stm32l1 - implemented BlueNRG SPI protocol
stm32l1 - bluenrg formatting fixes as advised by @farcaller
stm32l1 - refactored SPI enums and error codes
stm32l1 - minor formatting fixes to match the guidelines
Merge pull request #244 from kvark/spi

BlueNRG driver and demo app (based on STM32L1)