Internal faces are now correctly deleted and smooth shading is applied.

Fix: matrix operations
Based on report in anonymous forum.
Credits to: http://toro.2ch.net/test/read.cgi/cg/1361851855/570-571n

Fix: GUI layout, aligned buttons

New functionality: GStretch converts grease pencil strokes to vertices.

First commit via git, please don't shoot me if I did something wrong.