Readme : adding testing explanations

[glelouet]

@phax please make a pass to check if that is clear. The goal is to help other people, not make them more confused :D

[phax]

Looks fine to me. Do you want to add something on top of it?
Shall we add a statement on different Java versions, to use Maven profiles (I know I need to check the switch expression pr...)

[glelouet]

I think you're right, each feature should be documented. That would go in a dedicated doc/ folder though. Or docs / ? Or keep them at root / with .md to know they are doc ? I rather have them in dedicated folder, even though it makes links more awkard (starting with ../ )
Anyhow I rather have the root README.md cleaner with only simplest, most important things, but I agree that a nice doc goes a long way in helping people use a library more useful.

Now I don't think we should doc each feature about code, as those are better kept up-to-date with tests.
However I think a few features could be made tests for in the new jcodemodel-tests module since that contains both the generating code, and the generated resulting classes.

I made it a draft and will think about it once you give your opinion about the location, and the creation of additional test/example classes. Should I make an issue ? This way we can list what we want.