ResourceId and PageSize parameters, plus simplification of the FutExceptions

I have made some changes, some of them you may find very useful.

The most impacting changes are:
- The ResourceId and PageSize parameters of the SearchRequest;
- The refactoring of the exceptions and FutErrors, now only one class FutError exists (This was initially because ExpiredSessionException was using a FutErrorWithMessage when it should be using a FutErrorWithDebugString, so I've decided to unify both errors, in case EA changes any of them in the future).

The rest of the changes do not have that big of an impact, but they are still nice to have, I guess...