Remove check for Type::typeName() method when retrieving a type's typename

The smtk::common::typeName<>() function's logic has been modified to no longer check for the existence of a virtual std::string typeName() const method associated with objects passed as the template parameter. The check was removed to avoid the case where derived classes were inheriting their parent's typename, resulting in unexpected behavior (instead of either a compile-time error or a run-time exception).