feature: add more advanced setSimpleName that also changes the references

Hi everyone,

I find that really counter intuitive that the reference are not considered as `CtNamedElement`: for example, recently I wrote a processor to rename element in Spoon, in order to do it properly I also had to rename references, then it led me to the creation of a processor of CtElement with ugly casts to finally call the same methods `getSimpleName`/`setSimpleName`.

I know there is an historical reason for that and it would break a lot of things to change the metamodel to make CtReference inherits from CtNamedElement. I also know that @monperrus point of view on that is - if I remember well - that the reference should be computed from the structural elements and not directly modified by the end users.

However I really have the feeling that the current API does not allow to easily change only structural elements: for refactorings, we need to fix the references too.

So, I see at least two solutions here:
1. to make another interface maybe called `CtAbstractNamedElement` for `CtReference` and `CtNamedElement`: we keep the fact that `CtNamedElement` are structural elements, but we also allow to do lots of renaming/filtering by name, in using the same type
2. a completely different solution: we use internally in Spoon the model change listener to fix the reference when we change a name of a structural element. It won't help for querying the model, but it can surely help when refactoring.

Actually we might even apply both solution.
Is it a problem you also encountered using Spoon or is it just me? And WDYT about those solutions?