Yet another revision of aspect-ratio handling.
patch to prevent stroking zero-width lines in svg
Quick hack to make colorbar work with ps backend and 256 colors.
added set current image to pylab
Simplify axes.draw by using zorder more; add frame line on top.
Documentation for colorbar positioning change.
Bugfix in colorbar axes repositioning code.
Fixed bugs in revised color handling, quiver.
Make collections accept flexible mpl color specifications.
reverted is_scalar
