Convert Scene Tree to TSX

[MKHenson]

As part of the migration we need to convert the scene graph into TSX

• [x] Ensure group nodes can be created, deleted and store instances
• [ ] Ensure all resources load on scene startup and are removed on close
• [ ] Ensure all templates load on startup and are removed on close
• [ ] Ensure all context menu items have been implemented from previous class (pre TSX)
• [ ] Ensure all drag drop functionality has been implemented