Use the original separator text between unmodified nodes.

* Greens 8 more wt2wt tests

* TODO: Clean up. To be done in a follow-up patch so we can RT test this.

* Some pages no longer have RT errors
  - en:Pegi
  - en:Opinions of the Supreme Court of Canada by Chief Justice McLachlin

  Some others have a few more RT errors that might need investigation
  - en:Feature Driven Development

Change-Id: I6bcced762b9b36390cc926e3304c5516cd055c70