Give IMarshalerDelegate.getModelClass access to data.

I don't know what the official reasoning here is, but I found the properties string that getModelClass() would receive quite useless. Note only does this require parsing/regex to properly check for the presence of any property, but you also cannot differentiate based on the maps values, which might well be the most interesting use case.

This passes the original data object along as well, as a second argument, so it's backwards compatible.