Added host-based I2C C++ unit tests BREAKING CHANGE: I2C C++ interface changes, raw values for arguments are mostly not allowed anymore.
* spi cxx unit test (CATCH-based, on host) * added portmacro.h to driver mocking * added simple testing app to write/read SPI, using an MPU9250
* Wrapper class for simple GPIO interaction like read/write without ISRs. * Added rule to provoke builds after changes in the experimental C++ component.