documentation update
removed documentation builds from repo.

Fixed a few bugs in AxisItem

Moved GraphicsScene to its own directory, added exportDialog
Removed old export options from PlotItem / ViewBox (will re-enable once they are working again)

 - volumetric rendering
 - isosurfaces, mesh rendering
 - basic transformation and parent/child functionality

 - rotate/scalable view widget
 - volumetric data item

 - disabled opengl (performance issues in Qt 4.7)
 - numerous caching changes (disabled deviceCoordinateCache due to performance issues)
 - speed up loading large images in ImageView
 - bugfixes from Ingo Breßler
 - Transform rotation bugfix
 - Added debug module
 - Major performance enhancements for scatterplot, fixed point clicking issues
     ** API change for scatterplot click signals
 - Drawing on ImageItem is working well now
 - PlotItem downsampling no longer uses scipy.signal.resample (this was creating artifacts)
 - Fixed ViewBox behavior when aspect-locked

 - numerous fixes in close() functions
 - added Transform class
 - ROI widgets now operate in degrees instead of radians for easier Qt compatibility

Implements single axis scaling by mouse wheel over tick marks

  - converted most old-style signals into new-style for PySide compatibility (beware: API changes)
  - removed ObjectWorkaround, now just using QGraphicsWidget
  - performance enhancements, particularly in ROI.getArrayRegion
  - numerous bugfixes

  catched earlier by an item implementing this. Test it at the empty space 
  where the auto button appears in the plot window or on the scaleItems.
  Which element does this panning by default? parents: scene or view?

 - Lots of bug fixes
 - API change in PlotItem.plot(...)
 - Started replacing QObjectWorkaround with QWidget
 - Made plotCurveItems clickable
 - Added curve-following arrows

  (test_PlotWidget.py, test_MultiPlotWidget.py)
  (ubuntu 10.10, python 2.6.6, qt 4.7.0, pyqt 4.7.4, numpy 1.3.0)

added scatter plots

 - added vertical lines / regions for plots
 - added gradient editor widget
 - many bugfixes
 - cleaned up imageview a bit