Patch for scatter to allow linewidths to be specified.

Attached is a patch to the axes code that adds an extra

    > paramter, linewidths, to the scatter method.

    > My motivation for this wa I didn't want the black borders
    > around all the points in my plot.

This is a common wish -- just as a warning, using a linewidth of 0
does not work across backends; for example, I think it fails on PS.

The standard way to do it is to set the edgecolors to be the same as
the facecolors. To support this, I also added a boolean kwarg,
faceted=True and when False, sets the edge colors to be the same as
the facecolor. I also added your linewidth changes. revision 1.103 or later ...