webapp: Fix UI for removing XMPP connection.

templates/configurators/delete/xmpp.hamlet

@@ -0,0 +1,10 @@
+<div .span9 .hero-unit>
+  <h2>
+    Disconnecting from Jabber
+  <p>
+    This won't delete the repository or repositories at the other end
+    of the Jabber connection, but it will disconnect from them, and stop
+    using Jabber.
+  <p>
+   <a .btn .btn-primary href="@{DisconnectXMPPR}">
+     <i .icon-minus></i> Disconnect

templates/configurators/xmpp.hamlet

@@ -25,6 +25,8 @@
         <div .form-actions>
           <button .btn .btn-primary type=submit onclick="$('#workingmodal').modal('show');">
             Use this account
+          <a .btn href="@{DisconnectXMPPR}">
+            Stop using this account
 <div .modal .fade #workingmodal>
   <div .modal-header>
     <h3>