Feature system from json

New feature to build the physical components of a system using nested JSON configuration files. Within JSON file, if the component is meant to be a physical component include the "self" fields and specify dimensions in cm. Otherwise, don't include the self field. Additionally you can reference child components in the "children" field specifying their relative positions and rotations. Examples of the correct JSON format can be found in the JSONConfig/Frontier directory. What actually is spawned in the scene depends on what's in the cluster.json file in the JSONConfig directory.