fixed the Pen None property.

- https://groups.google.com/forum/#!topic/pyqtgraph/t6cl1CevlB0

Signed-off-by: Nicholas Tan Jerome <nicholas.jerome@kit.edu>
Fix memory leak in GLScatterPlotItem

Fixes #103. If a ScatterPlotItem was removed from a plot and added
again, glGenTetures was called again unneccesarily. Each time it is
called, it eats up a little more space.
Fix attributeerror when using spinbox in parametertree
Correction for spinbox auto-selection without suffix
Add recursive submenu support for node library.
fixed missing namespace.
Test submenu creation in example
Merge remote-tracking branch 'origin/develop' into develop

Conflicts:
	pyqtgraph/graphicsItems/ScatterPlotItem.py
	pyqtgraph/widgets/SpinBox.py