Doxygen autodoc for hardware architectures proposal

[Fabien]

Proposal would be to add a doxygen configuration file to generate documentation in the arduino hardware architectures folders (maybe one per architecture to start ?)

I attached a snapshot of what it is as a proof a concept for now, much more to be done if we agree on the proposal:

see my prototype changes in https://github.com/fab672000/Arduino/commits/master

Note that a documentation folder encapsulates all docuumentation config and generation so that the root does not get polluted by more content as we go, should be highly relocatable if it makes sense as an example to group architectures later.