Path expansion.

[fryguybob]

The expandPath function should be called scalePath. In its place should be real path expansion. For a non-closed path this is essentially stroking with a constant brush. For a closed path we can either give a path that has both the outside expansion and a negative inside expansion or just give the outside or inside (probably based on positive or negative radius). There are many options for what to do here and we should support several of them. Bezier curves have no closed form expansion with a single segment and as far as I know multiple segments can only approximate. There are lots of weird corner case, but if the end goal is to just fill it isn't very hard to get it right with a winding fill mode. For a cleaner path most of the corner cases can be handled by just considering adjacent segments.

I've got most of the work done for a few styles of corners for non-closed paths at this point. The rounded corner paths and polygons #36 is related to this issue.

[fryguybob]

This is closed by 01075fd.