MPU library
Added support for both SPI and TWI hardware drivers. The drivers are located in nrf_drv_mpu_spi.c and nrf_drv_mpu_twi.c respectively. A library is running on top of the drivers. The library is located in app_mpu.h/c. By using the library the hardware driver is transparent to the application and it is easy to switch between SPI and TWI.
- Fixed bug with nrf52 easydma examples.
- Added examples with MPU data sent via UART over BLE