Have the renderer page use a cell system

[Sixmorphugus]

Currently the renderer page uses a row/column system, meaning that the width of a row is the widest sprite in that row.
This wastes more than a bit of page space.
I propose a cell system that will subdevide the renderer's page into a list of all the empty square spaces - this list will increase in size by at least 1 whenever something is drawn inside a cell into which it fits.