matplotlib Code

documentation work

added documentation for usetex
added a static_figs directory for scripts that require optional features
to generate images for the documentation

Fix bug in Axes.scatter to make scatter-star_poly.py demo work

Fix bug in handling "close" option of Axes.fill

Fix bug in last commit and in matplotlib.use

List backends only in rcsetup

documentation updates

fix some formatting in documentation guide

updated documentation guide

updated doc outline