[Doxygen] Call tutorials "code examples" as on the website

compensate longer button title shortening "ROOT Home Page" to "ROOT Home"

documentation/doxygen/DoxygenLayout.xml

@@ -2,9 +2,9 @@
   <!-- Generated by doxygen 1.8.6 -->
   <!-- Navigation index tabs for HTML output -->
   <navindex>
-    <tab type="user" url="http://root.cern.ch" title="ROOT Home Page"/>
+    <tab type="user" url="http://root.cern.ch" title="ROOT Home"/>
     <tab type="mainpage" visible="yes" title=""/>
-    <tab type="user" visible="yes" title="Tutorials" url="group__Tutorials.html"/>
+    <tab type="user" visible="yes" title="Code Examples" url="group__Tutorials.html"/>
     <tab type="modules" visible="yes" title="User's Classes" intro=""/>
     <tab type="namespaces" visible="yes" title="">
       <tab type="namespacelist" visible="yes" title="" intro=""/>