Fix for complex live Editors

For reasons I'm not entirely sure about, my more-complex structure
causes the standard XML parser to crap out -- it appears to be decent
Xhtml, but not legal XML.

Fortunately, finally found scala.xml.parsing.XhtmlParser, which I've
been looking for.  This allows me to properly turn my HTML into XML for
manipulation, and makes a bunch of previous error cases legal.  We're
not yet doing the right thing with them, but at least they aren't
throwing errors any more.