Build and run unit tests during CI

[aentinger]

#118 contains host buildable and executable unit-tests which test the OTA business logic. This unit tests shall be built and executed upon a commit to master or any other branch and failure to build the unit tests or the occurence of an error during execution shall be back-propagated to the user.

Instructions for building the unit tests:

cd extras/test
mkdir build && cd build
cmake ..
make && bash -c bin/testArduinoIoTCloud

[aentinger]

Fixed due to merging #121.