Add CMake, doxygen, and coverage test files

Toolchain is now implemented. It generates shared library, unity and coverage
tests, and doxygen documentation.

'build_dev_version.sh' shell script is only here for developement purpose, and
comes with no warranty. It allows to generate an html summary of coverage tests
, and cleans the project after building time.

README has been modified, and program is now under GPLv3 licence (see COPYING
 file).