Migrate trailing nls across marker meta nodes.

* We can migrate trailing newline-containing separators
  across meta tags as long as the metas:
 - are not literal html metas (found in wikitext)
 - are not mw:PageProp metas (found in wikitext)
 - are not mw:Includes/* (cannot cross <*include*> bdry)
 - are not tpl/ext start/end markers (cannot cross tpl/ext bdry)

* Fixes RTing of this snippet
----------
{|
|a
|
|{{Party shading/Federalist}} | a
|}
----------

* Eliminates semantics diffs from en:Delaware gubernatorial elections

Change-Id: I4f2424c9b603db9cbe2bba2be60fca97d7e4024f