Lots of work on the display system, focused on pylab stuff. * Moved the pprint attribute to PlainTextFormatter. * Added DisplayFormatter.plain_text_only for disabling all but the plain text formatting. This is now used by doctest_mode. * Remove result_display hook. * Fixed doctest_mode magic. * Refactored inline matplotlib backend to use new display system. * Added display formatter for matplotlib.figure.Figure objects. so the display system will show the svg for them. * Added display and display_png to the user's namespace in pylab. * Cleaned up pylabtools.py