Add tutorial to Doxygen menu

docs/DoxygenLayout.xml

@@ -3,6 +3,7 @@
   <!-- Navigation index tabs for HTML output -->
   <navindex>
     <tab type="mainpage" visible="yes" title="Introduction"/>
+    <tab type="user" url="quick_guide.html" title="Tutorial"/>
     <tab type="pages" visible="yes" title="Guides" intro=""/>
     <tab type="modules" visible="yes" title="Reference" intro=""/>
     <tab type="filelist" visible="yes" title="Files"/>