Mirror-Function for editing rooms

Hi!

One of the more tedious issues is to have to redesign an entire room just because you want a flipped version of it.

It would be completely sufficient to just have one flip-axis, either by camera orientation or ingame's "North".
Hit [T] (if it's still free), since it is right next to [R] and also looks like a symmetry axis as a letter, and thus flip the room vertically.