Move all private symbols to private code and libs, add Unit tests
- A reorganization of the code, to move all the private stuff to fpi-*.c files and compile all this into a static libfprint-private lib
- added a stand-alone library for drivers (so no need to export anymore
fpi_get_driver_types
) - added lots of unit tests for devices (added a fake driver for that), context and state-machine
- Enabled gcovr reports, so we can get something nice (we were at this level before, so went from 44.8% to 52.8%!).
- various random fixes
- rebuilt the image using a more meaningful tag