New VECT format.

[fowler]

Looks cool!

Right now, lines are represented as closed by listing them with a
negative number of vertices.  I've found this to be slightly annoying
to try to program around (also, I've never found that it made much
conceptual sense).  If the vertex format is going to get completely
switched around, might it be possible to change this?

The combination of per-vertex and per-line colors is really neat.
I have an aversion to formats that are not blind to whitespace (ie
putting a carriage return in between the location of a point and the
color at that point would totally change the meaning).  This will also
mean that internally every point and every line must have a flag
saying whether or not it has a color.

Another comment on the current internals - I've found that trying to figure
out which colors belong with which points belong with which lines is 
nightmarish.  Figuring out which points belong with which lines is
also a bit annoying, but not that hard to do.

-Celeste