Predictably Random Z-levels and the SPACECUBE

The layout of the accessible z levels in relation to each other are now lain out in a massive preshuffled SPACECUBE. Every Z-level is no more than two screens from every other Z-level, and can be moved through in a predictable order* with a little ingenuity

*Except z.6

See pull for the full details
Adds z.7 (dead space 2) to boxstation because no one seemed particularly offended by the idea. This closes the cube properly there and prevents a few weird edge cases where closed loops of Z.6 to Z.6 transitions could happen.

Meta/Mini should add empty z.7 at some point after this pull is committed, I would have done so myself but it didn't play nice with mapmerge so I decided against it.
Whoops, made a dumb mistake
Adds the CUBElog
Merge pull request #4960 from Incoming5643/zlevel

[map] Predictably Random Z-levels and the SPACECUBE