ZResource and ZFile.ParseXML code should be refactored

[Kenix3]

ZResource and it's descendent classes should use more polymorphism. There is not a huge amount of consistency in method names right now for the extraction code entry point. This should be an overridden method from ZResource for each type.
Further, the code in ZFile.ParseXML for each type should be moved to a method in ZResource and overridden methods.