[ ] Resize divs/canvas elements by dragging at the edges
[ ] Dynamic resizing of elements when the screen size changes
[ ] Vertical resizing so that we fill 100% of available screen space (this is done for widths currently, but heights are hardcoded in pixels in the css)
[ ] Close a div/canvas by clicking an x at the top right (and they will come back by dropping an appropriate file back onto the screen?) (LOWEST PRIORITY)