Adds ability to define tile sub-cells in mod.yaml

Implements #6086 - Number and offsets of SubCells should not be hardcoded
Actually, the first one defines the offset for an actor using the full cell.
I wrote it that way to load an array with index 0 being the full cell since 0 is the index for using the full cell. Yes, that does allow modders to shift actors using the full cell too.