Eeschema: add schematic sheet page number.

The groundwork has now been laid for per sheet instance data.  Initially
this only supports sheet page numbers but could be expanded to include
other per sheet instance information.

ADDED: Support for user defined schematic page numbers.

pcbnew/plot_board_layers.cpp

@@ -847,7 +847,7 @@ void PlotSolderMaskLayer( BOARD *aBoard, PLOTTER* aPlotter, LSET aLayerMask,
 
     // Remove initial shapes: each shape will be added later, as flashed item or region
     // with a suitable attribute.
-    // Do not merge pads is mandatory in Gerber files: They must be indentified as pads
+    // Do not merge pads is mandatory in Gerber files: They must be identified as pads
 
     // we deflate areas in polygons, to avoid after subtracting initial shapes
     // having small artifacts due to approximations during polygon transforms
@@ -1108,7 +1108,7 @@ PLOTTER* StartPlotBoard( BOARD *aBoard, PCB_PLOT_PARAMS *aPlotOpts, int aLayer,
         if( aPlotOpts->GetPlotFrameRef() )
         {
             PlotWorkSheet( plotter, aBoard->GetProject(), aBoard->GetTitleBlock(),
-                           aBoard->GetPageSettings(), 1, 1, aSheetDesc, aBoard->GetFileName() );
+                           aBoard->GetPageSettings(), "1", 1, aSheetDesc, aBoard->GetFileName() );
 
             if( aPlotOpts->GetMirror() )
                 initializePlotter( plotter, aBoard, aPlotOpts );