Option to not generate emissive nodes in Prep Materials

[StandingPadAnimations]

Work on this feature began in Kaion, and now I'm just refining this feature.

This adds an option to prep materials to not add emissive nodes, which can help to reduce noise in Cycles and makes nodes less complex in EEVEE.

[StandingPadAnimations]

Also yeah, I'm back. Kaion is just my fork that focuses on being a proof of concept as well as adding more features that rely on "experimental" (for the lack of a better term) things

[TheDuckCow]

Nice! Just careful that I think your readme got picked up over here too. Curious, what does Kaion mean? And let me know whenever you'd like me to review (by assigning me as a reviewer, per usual)

[StandingPadAnimations]

Curious, what does Kaion mean?

Kaion is part of the name for my old OC Kaiyona (which Kaion is derived from) from back when I did Minecraft rendering. I decided to keep it as a fun reference

[StandingPadAnimations]

And let me know whenever you'd like me to review

I'm actually almost done (in theory, I'm on a laptop that doesn't have Minecraft so it's a bit hard for me to test), I just need to figure out matgen_cycles_original (should be similar to matgen_cycles_principled, just with some extra nodes)

[StandingPadAnimations]

Due to some branch changes made a while back, a new PR has been made to track changes: #369