added panning plot example

Added MultiplePlotAxes example

  - Made numerically sortable
  - Added setEditable method
  - Added example

Move setSortingEnabled to the widget init rather than after setting the data, otherwise weird sorting happens

added experimental opengl line-drawing code

  - AxisItem did not update grid line length when plot stretches
  - Workaround for PySide/QByteArray memory leak

Workaround for PySide bug; fixes GradientEditorItem

cleaned up examples

CSV exporter gets 'precision' option

ViewBox: made padding more consistent for all auto-ranging methods, deprecated autoRange(item=) in favor of autoRange(items=)

Added imageview.setImage argument documentation