Hi Pilou, re: extrusion direction

This is a limitation of the current extrusion command - it only knows how to extrude in one direction at a time.

Eventually I would like to enable multiple-object extrusion where each object extrudes by default along its own normal. But that was a bit more difficult (especially with the mouse interaction, there would be sort of multiple possible tracking lines), so when I was working on extrude I postponed that until some later version.

- Michael