Changes for 2.0.12

• Fixed a memory leak with internal Picture caching when modifying Panel item arrays.
• Fixed animation when expanding and collapsing during Diagram load.
• Drawing fix for IE when drawing zero width or height geometries that have a stroke.
• The DraggingTool will no longer auto scroll the diagram if Diagram.isReadOnly is true or both Diagram.allowMove and Diagram.allowCopy are false. This means that, by default, a Palette will no longer auto scroll while the DraggingTool is active.
• Improved positioning of unrotated link labels when GraphObject.segmentOffset is  go.Point(NaN, NaN)  and the link segment is more vertical than horizontal.