Backport: Xinha: nested lists are broken after a save (CMS7-7084)

Nested listed can not be indent/outdented after a save. This is because Xinha delegates the indent/outdent action to the browser's execCommand which produces invalid HTML (all browser do except for Opera). After a save the HTML is fixed by the HTMLcleaner after which Xinha doesn't know how to do indent/outdent anymore.

The only solution to this is write a custom indent/outdent for ul and ol elements, like this one: https://raw.github.com/dojo/dojox/master/editor/plugins/NormalizeIndentOutdent.js