Bug 62323: Several tweaks to DOM passes to handle fostered content.

* 5 DOM passes were fixed up to be aware of fostered content.
  - Mark fostered meta tags with a fostered flag in data-parsoid.

  - Explicitly set DSR ranges to zero-width in DSR computation (not
    sure how I missed this when I implemented this -- I suppose because
    we were mostly dealing with simple cases where the right-to-left
    pass handles this correctly).

  - DOM fragment unpacking has to be aware fostered content and not
    overwrite zero-range DSR width.

  - Fix to migrate trailing newlines pass to not migrate newlines out
    of foster boxes.

  - Template encapsulation sets dsr range to zero-width if the outermost
    wrapper node is fostered.

* Also fixed the "temporary" fallback code in serializer to not run
  on fostered content. We should probably get rid of the silly fallback
  and see what fails and fix the failures.

* RT test results:
  - One selser test now passing.
  - 2 more failing -- related to missing data-mw for which the fallback
    scenario exists. I am going to separately investigate a fix for the
    missing data-mw problem (seen in some contrived fostered template
    scenarios).

* http://localhost:8000/_rtselser/enwiki/Dancing_with_the_Stars_%28U.S._TV_series%29?oldid=598141704
  now RTs with just a missing newline.

Change-Id: I94d471b381edfbe58dd13dbf9a10b5687bde71e2