Moving controls several steps by holding down arrow keys is now working again.
Removed canvas special handling in DesignPanel and instead letting each placement behavior handle its own special needs, and handling the Canvas issue by overriding GetPosition in CanvasPlacementSupport instead.
Fixed SetPosition in CanvasPlacementSupport so Left/Top properties have priority over Right/Bottom, as this is the priority that the runtime uses.
Merge pull request #501 from gumme/WpfDesignerCanvasPlacementFix

Wpf designer placement fixes