CForest new version

Do not focus on the documentation, I am leaving it for the end since there are a lot of changes and probably more to come.
To activate CForest here makes things much easier. For instance, in RRTStar, the IntermediateSolutionCallback is only called if CForest is activated. If we do not activate it, includeValidPath will never be called. And I cannot think in any other way right now on how to implicitly activate CForest. Maybe, once we solve the problem with the sampler we can do something.