fix bug in nonmanifold edge swap
fix bug in nonmanifold edge swap

most of this was set up correctly,
but the loop gathering algorithm
would travel a full 360 degrees
around the edge for both halves.

this may not be the clearest
solution, but have it stop when
it crosses from one geometric
region to another.

YetAnotherMinion/core,yangf4/core,YetAnotherMinion/core,yangf4/core,yangf4/core,yangf4/core,YetAnotherMinion/core,YetAnotherMinion/core,yangf4/core,YetAnotherMinion/core