updated Mike's fancy plots to v1.2.0

From: Michael Nowak, http://space.mit.edu/cxc/isis/archive/2011/0766.html
Date: Sat, 19 Mar 2011 23:04:53 -0400

I have added a plot option, gap, that changes the way models get plotted.

   plot_{data,counts,unfold}(1;gap={1});

and you get the usual behavior - models don't plot through the data gaps,
and are histograms.  If instead you do:

   plot_{data,counts,unfold}(1;gap={0});

and then the model plots by bin centers, and happily (linearly) plots through
gaps. It's not a perfect solution, but I actually had kind of wanted something
like this for plotting models through radio data (where we just have widely
separated bin centers usually).

There are a bunch of other tweaks in there, too, to the routines.  A few bug
fixes.  And I've changed the way the no_reset behavior works.  As a
graduation present to Manfred, it now works as a qualifier, not a global
variable.  (This breaks some backwards compatibility, but such is life.)  If this
part makes no sense to you, don't worry about it and ignore it.  Everything
else works the same as before.

Also, thanks to some tweaks of Manfred to the write_plot routine, the plotting
routines no longer need to be invoked in their own namespace.

If anyone finds any bugs, let me know.

-Mike