Cleanup & add compiler warning options.

[ArthurSonzogni]

• Add compiler warning. This avoids common problems.

• Add a top-level CMakeLists. This allows developers to know they can use CMake and can directly use cmake using cmake .. from the build/ directory, instead of cmake ../board.

• Merge the few Makefile into a shorter one.

• Remove the bin directory. Output directly into the build directory.

• Add tools/format.sh to run clang-format on every files.

• Format every files.

[SAtacker]

Beagle-config has a host part that might be using Qt. That's why I had it under the board directory. I'll have a new repository for the host if that's bettter.

[ArthurSonzogni]

Yes. And we can move the content of src/ into src/board when you will add the src/host. I can rename if src/ board/ if you really care about this. Please let me know.

[SAtacker]

I'll do it later and add an option in CMakeLists.txt