usability improvements

only one column is editable at a time
editable columns have a different appearance from locked columns
any column can be edited by anyone via an edit button
columns and rows require confirmation before deletion

www/poll/index.html

@@ -62,7 +62,7 @@
             <thead>
                 <tr>
                     <td>
-                        <div id="adduser"></div>
+                        <div id="adduser" class="clickable" title="click to add a user">+ Users</div>
                     </td>
                 </tr>
             </thead>