WIP A lot of reformatting, especially inside the highlighting implementation
WIP Documentation on highlighting
WIP Completed documentation and did a bit of refactoring as well.
WIP Deep refactoring of highlighting.

Might be a bit broken, switching now to testing before coninuing on that!
WIP Simplified a lot the code.

I put more persistsent data and convenient methods in BaseRule (formerly Container). This led to more simple and semantic code, less prone to error.
WIP Continued the factorization of code for highlighting.

I also added some debugging code (could be improved, or even deleted later), that permitted me to quickly fix an infinite loop in the Key rule. A wrong loop termination condition.