tags.py: Don't add props to subclasses; GCTag: get allowedSubTags from parent; GCObjectSwizzling: test entire hierarchy to find best class for property
GCObjectKeyValueMethods: use allowsMultiple on self instead of gedTag
GCTag: Cleanup, check if valid in allowedOccurrences
GCObject keyPathsForValuesAffectingValueForKey reworked sice there's now a class.gedTag
GCTagAccessAdditions: reorder some methods
GCNodeParserDelegate methods aren't optional
GCNodeParser: parsedNodes property if you don't want to use the delegate methods.
GCContext: Not a GCNodeParserDelegate