Combine splines node

But yeah. even just TWO INTO ONE allows /n/ into one eventually. With no way to combine splines and as far as I can see no easy way to just create seg splines from "scratch" it's clear we will want to expand the toolset in that area anyway. Faster to just write a few than to tie you up in writing some.

EDIT: but if you waaaaant to provide some kind of ninja fast implementation.. Hell go for it. (I think i saw some Den.Tools about arrays that looked likely to use for splicing, I would've just used them based on examples from extant code that does merging, think I saw some of them too) https://forum.unity.com/threads/released-mapmagic-2-infinite-procedural-land-generator.875470/page-28#post-7341704