StructuredLabels/Data refactoring: Replace CSGObject by SGRefObject

* Changed base class of `StructuredData` from to `SGRefObject`
* StructuredLabels now using `DynArry<StructuredData*>` instead of `DynamicObjectArray`, because the latter can only hold `CSGObjects`
* (updated a lot of files to reflect name changes, including SWIG mappings)