documentation/poky-ref-manual/poky-ref-manual.xml: Added Title tag

The title of the document used to create metadata for output formats
such as eclipse help.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/ref-manual.xml

@@ -16,7 +16,9 @@
             </imageobject>
         </mediaobject>
 
-        <title></title>
+        <title>
+            The Yocto Project Reference Manual
+        </title>
 
         <authorgroup>
             <author>