Add setUserIndex/getUserIndex (int index) to btCollisionShape

Share physics setup of BasicDemo between different graphics frameworks, see Demos\BasicDemo\BasicDemoPhysicsSetup.*
Plan is to do this for all Bullet demos.
Improve gwen performance and cursor navigation for tree control.
tweak shadowmap size
SimpleOpenGL3App::registerCubeShape accepts half extents

btgui/Gwen/Controls/ScrollBar.h

@@ -61,6 +61,16 @@ namespace Gwen
 
 				Gwen::Event::Caller	onBarMoved;
 
+				float getContentSize() 
+				{
+						return m_fContentSize;
+				}
+				float getViewableContentSize() const
+				{
+				
+					return m_fViewableContentSize;
+				}
+
 			protected:
 
 				ControlsInternal::ScrollBarButton* m_ScrollButton[2];