We had many context menus with names, simply because you were forced to give them names.
Painter gains the ability to draw lines with arbitrary thickness. It's basically implemented by drawing filled rects for thickness>1. In PaintBrush, Tool classes can now override on_contextmenu() to provide a context menu for the toolbox button. :^)
Could do with some more tweaking no doubt, and it'd be nice to have a circular spray, but this is better than nothing.
Also add a Tool base class, and an empty BucketTool subclass which is the next thing to implement.
