Generate Custom Model - Support for 4-channel nodes (work-in-progress)

[tbuaas]

Hi xLights devs! Huge fan here, and hoping to contribute!

I picked up some "Twinkly RGB+W" 600 string on clearance, and wanted to generate a custom model in xLights similar to what Twinkly does themselves with their app. I found that this would not work out-of-the-box with xLights, as the code seems to assume the controller accepts RGB (3-channel) input.

I hacked up some code and got it to work with the RGB+W lights, so I think I would like to contribute this to the community. I am seeking guidance on how to rewrite it to be most useful.

Rather than just a simple 3-channel/4-channel selector (which does not appropriately distinguish WRGB vs. RGBW nodes), my intuition is that the "color order" drop-down with RGB/GRB...WRGB/WGRB...RGBW.. would be more universally useful for various situations (perhaps with even a mode for single-color (white only) addressable nodes?). I did not see something obvious I should re-use in the code to do this (color order list), but am happy to do whatever works best for the project and the community.

TL;DR: Want to contribute 4-channel support to "generate custom model", seeking advise on how to finalize this contribution for acceptance.

No rush to respond, just hoping for some guidance. Cheers!
Tom Buaas