- images should be relative to project path 
  simply ask for "relative?" at image loading
  (search for find-relative-path in controller.ss
  and modify pwig:file% in property-widgets.ss)
- "paste before", "paste after" : avoids recreating the whole thing for each move
- widget: array/grid panel
- widget: board canvas
- widget: columns-box% from Towers
- doc: add doc for 'post-code' (plugins) and 'show-at-init' and 'code-gen-class'

- change name to GRacket Designer ??