drivers: added low-level I2C driver interface
cpu/stm32f1: added low-level I2C driver
board/iot-lab_M3: added I2C device definitions
board/iot-lab_M3: added features
tests: added i2c driver test
Merge pull request #1785 from haukepetersen/add_stm32f1_i2c

cpu/stm32f1: added I2C interface&implementation
drivers: added driver for ISL29020 light sensor
board/iot-lab_M3: added ISL29020 interface defs
tests: added test for ISL29020 light sensor driver
Merge pull request #1786 from haukepetersen/add_driver_isl29020

drivers: added driver for ISL29020 light sensor
Initial import of nrf24l01p lowlevel functions
[SQUASM ME] removed tests/test_spi
[SQUASH ME] changed delay after function call
[SQUASH ME] update some small things to changes caused by netdev in another PR
[SQUASH ME] added a small REAMDE to describe the usage of the test
[SQUASH ME] whitelist arduino-due for nrf24l01p lowlevel test
[SQUASH ME] style fixes
added msg_send function from rx-interrupt to thread
added documentation and changed some functions return types
[SQASH ME] removed spi transfers during ISR