reporting: add new background layer

@graph/writeGraphFile.m

@@ -194,18 +194,18 @@ if ~isempty(o.shade)
                         date2string(o.shade(1)) ' or ' date2string(o.shade(end)) ' is not in the date ' ...
                         'range of data selected.']);
     if x1 == 1
-        fprintf(fid,['\\begin{pgfonlayer}{background}\n\\fill[%s!%f]\n(axis ' ...
+        fprintf(fid,['\\begin{pgfonlayer}{background0}\n\\fill[%s!%f]\n(axis ' ...
                      'cs:\\pgfkeysvalueof{/pgfplots/xmin},\\pgfkeysvalueof{/pgfplots/ymin})\nrectangle (axis ' ...
                      'cs:%f,\\pgfkeysvalueof{/pgfplots/ymax});\n\\end{pgfonlayer}\n'], ...
                 o.shadeColor, o.shadeOpacity, x2);
     elseif x2 == dd.ndat
-        fprintf(fid,['\\begin{pgfonlayer}{background}\n\\fill[%s!%f]\n(axis ' ...
+        fprintf(fid,['\\begin{pgfonlayer}{background0}\n\\fill[%s!%f]\n(axis ' ...
                      'cs:%f,\\pgfkeysvalueof{/pgfplots/ymin})\nrectangle (axis ' ...
                      'cs:\\pgfkeysvalueof{/pgfplots/xmax},\\pgfkeysvalueof{/' ...
                      'pgfplots/ymax});\n\\end{pgfonlayer}\n'], ...
                 o.shadeColor, o.shadeOpacity, x1);
     else
-        fprintf(fid,['\\begin{pgfonlayer}{background}\n\\fill[%s!%f]\n(axis ' ...
+        fprintf(fid,['\\begin{pgfonlayer}{background0}\n\\fill[%s!%f]\n(axis ' ...
                      'cs:%f,\\pgfkeysvalueof{/pgfplots/ymin})\nrectangle (axis ' ...
                      'cs:%f,\\pgfkeysvalueof{/pgfplots/ymax});\n\\end{pgfonlayer}\n'], ...
                 o.shadeColor, o.shadeOpacity, x1, x2);

@report/write.m

@@ -71,9 +71,9 @@ fprintf(fid, '\\renewcommand{\\bottomfraction}{0.8}\n');
 fprintf(fid, '\\setlength{\\parindent}{0in}\n');
 fprintf(fid, '\\newlength\\sectionheight\n');
 fprintf(fid, '\\begin{document}\n');
-fprintf(fid, '\\pgfdeclarelayer{background}\n');
-fprintf(fid, '\\pgfdeclarelayer{foreground}\n');
-fprintf(fid, '\\pgfsetlayers{background,main,foreground}\n');
+fprintf(fid, '\\pgfdeclarelayer{background0}\n');
+fprintf(fid, '\\pgfdeclarelayer{background1}\n');
+fprintf(fid, '\\pgfsetlayers{background0,background1,main}\n');
 fprintf(fid, '\\centering\n');
 
 nps = length(o.pages);