- fixed issue with basic (empty) objects acting as containers
- cleaned up some of the inheritance , custom element callbacks
- added functioning support for selection helper (for object selection/hovering etc)
 * use a special attribute "hierarchyRoot" to specify where to traverse the object hierarchy
 * minor cleanups

- added support for multiple scenes
 * make use of custom attributes
 * cleaned up 'default' scene fetching

- more minor cleanups