Started Python3 compatibility changes

GraphicsScene/GraphicsScene.py

GraphicsScene/__init__.py

GraphicsScene/exportDialog.py

Point.py

Qt.py

SignalProxy.py

Transform.py

WidgetGroup.py

__init__.py

canvas/Canvas.py

canvas/CanvasItem.py

canvas/CanvasManager.py

canvas/CanvasTemplate.py

canvas/__init__.py

configfile.py

debug.py

dockarea/Container.py

dockarea/Dock.py

dockarea/DockArea.py

dockarea/DockDrop.py