Migrate reference guide to well-formed docbook XML

Convert all docbook XML files to well-formed docbook 5 syntax:
 - Include xsi:schemaLocation element for tools support
 - Convert all id elements to xml:id
 - Convert all ulink elements to link
 - Simplify <lineannotation> mark-up
 - Fix misplaced </section> tags
 - Fix <interface> tags to <interfacename>
 - Cleanup trailing whitespace and tabs

Issue: SPR-10032

src/reference/docbook/swf-sidebar.xml

@@ -1,7 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<sidebar xmlns="http://docbook.org/ns/docbook" version="5.0"
-    xmlns:xlink="http://www.w3.org/1999/xlink"
-    xmlns:xi="http://www.w3.org/2001/XInclude">
+<sidebar
+    xmlns="http://docbook.org/ns/docbook" version="5.0"
+    xmlns:xl="http://www.w3.org/1999/xlink"
+    xmlns:xi="http://www.w3.org/2001/XInclude"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="
+        http://docbook.org/ns/docbook http://www.docbook.org/xml/5.0/xsd/docbook.xsd
+        http://www.w3.org/1999/xlink http://www.docbook.org/xml/5.0/xsd/xlink.xsd">
   <title>Spring Web Flow</title>
 
   <para>Spring Web Flow (SWF) aims to be the best solution for the management
@@ -18,6 +23,6 @@
   that drive business processes.</para>
 
   <para>For more information about SWF, consult the
-  <ulink url="http://www.springframework.org/webflow">Spring Web Flow website</ulink>.
+  <link xl:href="http://www.springframework.org/webflow">Spring Web Flow website</link>.
   </para>
 </sidebar>