Improve adding custom presets

[jlampel]

Ideally, lights should be grabbed from .blend files rather than python libraries.

• Categories can be made from collections.
• Lights should be created rather than appended for full flexibility, but values can be grabbed from the Cycles nodes or custom properties.

[kosirm]

That's super! Ideally with future blender asset manager it should be possible to save lighting presets. At least I hope so. Thank you so much for this amazing addon!