Allow moving entire floors

[tkindy]

Currently, the landings for other floors start pretty far away. This is to make sure that there's enough space for each floor to grow independently. However, it makes the early game pretty cumbersome because there's a lot of blank space to move around in to see the other floors.

With #18, placed rooms can be moved around, so the landings could start closer. If they start growing into each other, though, you have to individually move every room on the floors a space or two away to make room.

You should be able to move entire floors in one action. As part of this work, I can also start the landings closer to the ground floor.