added method that lets caller specify relation between spaced views

original method now calls the new one with NSLayoutRelationGreaterThanOrEqual as before

@ndonald2 I needed this functionality to have some labels display correctly when not pinning their widths; otherwise they'd shrink due to the >= relation of the spacing. This way I can set it to =
No, I don't think we need to put an ultimatum date in the message. How about whenever I get around to the "big" refactor of RZUtils, I will remove it. That's not going to be backwards compatible anyway (but I am going to create a "legacy" tag that existing projects can always reference for compatibility).