Fix Before and After css for string fields

* Make multi-lingual strings generate internal classless
  span elements for each language.
* Generate css that will properly handle before after and
  between for the new multi-lingual string xhtml.
* Headword has writing system options so use the
  multi-lingual virtual property (MLHeadword)

Change-Id: I896ae813363b65750fec4bd7114e33981568b1fc