Clean up changes outside rtNode

[jmgasper]

Lots of little changes have been made throughout the rest of the pxScene codebase.

The client wants to limit these changes as much as possible, so we need to:

1. Add support for missing features so we can rollback changes to pxScene / pxCore
2. Document why a change is needed

The client has looked at the changes so far and would like to try to limit the changes to rtNode as much as possible.