Import sample fragbuts.xml if user file does not exist

src/sampleconf/fragbuts.xml

@@ -1,8 +1,14 @@
 <?xml version="1.0" encoding="UTF-8"?>
+<!-- Example file for configuring the "Query fragments" window.
+     Each <buttons> or <radiobuttons> element defines a lines of buttons
+     Each active button adds a query language fragment to the current query
+     before execution. 
+-->
+
 <fragbuts version="1.0">
 
   <radiobuttons>
-
+    <!-- Actually useful: toggle WEB queue results inclusion -->
     <fragbut>
       <label>Include Web Results</label>
       <frag></frag>
@@ -23,20 +29,29 @@
   <buttons>
 
     <fragbut>
-      <label>Year 2010</label>
+      <label>Example: Year 2010</label>
       <frag>date:2010-01-01/2010-12-31</frag>
     </fragbut>
 
     <fragbut>
-      <label>c++ files</label>
+      <label>Example: c++ files</label>
       <frag>ext:cpp OR ext:cxx</frag>
     </fragbut>
 
     <fragbut>
-      <label>My Great Directory</label>
+      <label>Example: My Great Directory</label>
       <frag>dir:/my/great/directory</frag>
     </fragbut>
 
   </buttons>
 
+  <buttons>
+
+    <fragbut>
+      <label>Check the manual (Query Fragments Window section) for explanations</label>
+      <frag></frag>
+    </fragbut>
+
+  </buttons>
+
 </fragbuts>