Custom tool to use the mouse to pan and scroll an image window.

This tool allows the user to pan and scroll the image window interactively by dragging the image with the mouse. When invoked on a McGraphOverlay that is being displayed in an IMcView, the tool shows a hand icon whenever the cursor passes into the viewed client window. When the left mouse button is pressed and held (or mcpstcfStartPanScroll is assigned to CommandFlags), then the IMcView.Pan and Scroll properties are set to track movement of the cursor until the left mouse button is released (or mcpstcfStopPanScroll is assigned to CommandFlags).