keep track of active cells in PagedWorldspaceWidget and update SubView title accordingly
fixed scene toolbar layout problems
size adjustment
added grid tool (does not work yet)
increased scene toolbar button size
removed grid button (discarding the first attempt at a cell selector)
added CellCoordinates and CellSelection classes
replaced rectangular cell selection with a CellSelection object
allow multiple cell coordinates in c-type hint for scene subviews
Merge branch 'cellselect'