Don't process mw:dom-fragment-tokens in AttributeExpander

* The AttributeExpander was interfering with the content and
  processing it rather than leave them for the DOM Fragment
  handler.

* Was causing regressions in RT testing.
  Fixes fr:Constitution, de:Vincent_van_Gogh

* Added a couple new parser tests which should catch these kind
  of issues in the future. These are Parsoid-specific image
  tests (unbalanced tags in caption; tempalte transclusion in
  caption). Given different output for images for PHP parser and
  Parsoid, I made this Parsoid only for now. The html2wt tests
  fail because of data-parsoid getting stripped out.

Change-Id: Ia417e3f5f797b89e4913df663b594c2758f6498c