[ttml2] pre-fpwd-review-1 available for review

A snapshot of TTML2 is now available [1] for a 2 week review prior to FPWD
processing. I have not yet created a new SoTD. All issues against TTML2
currently marked open are documented inline in "Issue" boxes, of which
there are 23 cited. Embedded editorial notes (explicitly marked) indicate
additional editor tasks that don't necessarily have a corresponding issue.

Both these marked issues and editorial notes are intended to go out in the
FPWD as is.

[1]
https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2-20150114-pre-fpwd-review-1.html