object registry filtered objects uses derived name

Affects the implementation of csorted etc.

It checks the name from the cast pointer

matchName(ptr->name())

instead of from the object pointer

matchName(obj->name())

This only seems to affect finite-area directly, since the cast pointer will have "region0" as its name, whereas the object is actually registered as "faMesh". Cross-ref EP2297

Regression introduced with 95e2a2e8 but was not exposed until 129b7381 (develop branch)