Added functions to python objects to read their values from the FreeCAD objects
Added functions to python objects to parse their values into JSON format python dictionaries
Added logic to export the tree in the product assembly read_from_freecad and parse_from_freecad function (no traverser needed, because we can parse it recursive top-down)
-Added function in sheets to read from a FreeCAD sheet (not a document)
Implemented the exporter: