Add complex dCuboids

dCuboids can now be a list of cuboids rather than a single one - EG, you
can have ten different cuboid regions noted under a single name, or...
whatever use it may have.
Basically just finishing the implementation of the cuboid system.
Also, reverse 'cuboid.is_within[location]' to
'location.is_within[cuboid]' for the sake of clarity (and following the
rules of English)
Also, fix a few location and cuboid handling bugs