+ exportImage() now uses ImageExporter to export images without
  invoking the ExportImageDialog

+ Settings are preserved between the graphical UI and the D-Bus
  interface, so you can set up the legend settings graphically first,
  and then run a script to iterate over many objects.

+ exportImage() now accepts an optional flag that decides whether the
  legend must be added or not, irrespective of the settings last used
  in the graphical UI, for extra convenience.

BUG