Add methods to support generating color palettes

[mqole]

adds methods to Color.cs that support generating:

• complementary colors
• split complementary colors
• triadic palettes

(ANALOGOUS NOT INCLUDED)
EDIT: ANALOGOUS NOW INCLUDED

this pr is required for space-wizards/space-station-14#38528.

[AJCM-git]

return a color array

[dffdff2423]

See below.

I think you should also maybe add a basic unit test or two but that would be something up to the maintainers.

[metalgearsloth]

Could also really do with a test.

[mqole]

i think i did the angles properly, will need someone to check working.
EDIT: i do not think i did the angles properly

no idea how to write integration test. tried looking for examples in the codebase as well as slam's unmerged tutorial, but the tutorial is more geared towards content and all the codebase examples in robust i found were either 7 years old, inconsistently formatted to each other, or both.

EDIT 2: never mind im basically smart

[whatston3]

A few more thoughts.

I think the constants based on the angles you had before should work better (slightly more precise). The values you're testing could be based off of your constants, too.

Haven't tested the suggestions, all webedit ops, so do take care.

[mqole]

what i love to see!

[whatston3]

Reads fine to me, pardon the annoyance.

[Also, didn't say it yet but this is a very nice PR. Good stuff.]