Make it easier for inquisition subclasses to specify custom response classes.

I'm not totally opposed to doing it this way, but would have expected `getResponseWrapperClass()` to simply take care of this itself by just returning `SwatDBClassMap::get('InquisitionResponseWrapper')`. It seems simpler and I'm not sure the auto-magicness of the resolved class is obvious enough that we wouldn't end up wrapping the class in `getResponseWrapperClass()` with a class-map anyway by accident.