[split] Buffer Exchange cleanup script

[N. W. Perry]

Alternative to all this would be to implement the buffer exchange rules while looping the lines.

Well, that's where I'm at already. But I didn't think about trying getVisible—because obviously LDCad already knows the rules of buffer exchange, so it would be nice not to have to figure them out myself!

Downside is this function is only available on reference lines, and as you are looping all lines you will probably be working with the generic srcLine object.

I don't have to handle every line, or do I? The only lines I need to manipulate would be the ref lines.