cpp-checks, clang-format and doxygen documentation

This release improves in two areas.

• documentation
• code quality
  First, Doxygen generates a website from the code itself. Next, GitHub Pages host the final documentation. After that, all code is formatted with 'clang-format' according to LLVM C++ rules. Finally, 'cppcheck' automatically detects flaws, and lastly, all example sketches(s)
  are compiled and uploaded to target microcontrollers.
  It can be excessive work for such a tiny Library, but if the build system lacks the quality for small tasks, it will not be suitable for the next major project. Thus I see this as an exercise for coming libraries.