Revert "Moved all test items to z level 0. (floors have a height of 0, so items at the same z level as them will still be on top of them)"

This reverts commit 3cdf3910c51e53a286cdbe11f1ffc14b3c61ff6c.
Moved all floors to z level 1. (0 is reserved for divots in the floor)
Item falls of the map when it falls below z level 0.