Rename Border Collisions for MantaFlow Domain

Hi!

Currently, under border collisions for a domain object in MantaFlow, there is Front, Back, Right, Left, Top, and Bottom. I'm not sure what's meant by all of them (except I can guess top and bottom are probably Z+ and Z-). Wouldn't it make more sense to rename them to X+, X-, Y+, Y-, Z+, and Z-?