Single Key MouseModule Activation:
  X  zoom X
  Y  zoom Y
  V  slice Vertical
  H  slice Horizontal
  D  crosshair digitizer
  B  bookmarks
  E  edge detector
  F  frequency measurer


Should DragRenderers only be allowed to communicate science events?  If so,
then what is the purpose of a MouseModule?

2007-01-29: eew
   Ed suggests the mouseModules have a hook that is called when the MM is selected, so it can pop up a dialog, etc.

  