Control RGB LED lighting

[amorphic]

As a user I would like to control my printer's RGB LED lighting.

[amorphic]

For most firmwares we can control GPIO output pins using M42. Using simple on/off with RGB gives us 7 possible colors: R, G, B, C, M, Y, W, B.

Implement this as a set_lighting() with an argument color and valid values: red, green, blue, cyan, magenta, yellow, white, black

[amorphic]

This might be a good opportunity to create a plugin system.

Plugins which require frontend changes could do so via Vue.js components which are loaded dynamically.