replaced PropertyPanel with WebPropertyPanel

- Use DOM rather than Canvas for the property panel.
- Added the concept of a PropertyEditor which can be used to show/edit a
property (currently TextPropertyEditor and ObjectPropertyEditor)
- move SelectList into it's own file
- removed the SelectCommand (we no longer undo/redo selections)
- removed the PropertyTool, this is all handled by various
PropertyEditors
- RotateTool, MoveTool and ResizeTool now hide the selected objects on
the draw ctx, and draw them on the tool ctx
- Bounds and Transform now have clone() and copy() functions
- added some property styles for the WebPropertyPanel