Add new SPPM integrator support
Ordered code definitions
Add support for SPPM integrator.
Starting 'help' for SPPM
Delete some unused and deprecated code in lights.
Add 'mirror' color option to coated glossy material.
Delete deprecated and unused code.
Comment some parts of code for testing usability.
Add new entries for material help.
Refine SPPM code.
Add more options for 'spot' lights
Testing new UI distribution for 'coated glossy'.
Add mirror color option for coated glossy.