major update to inline regions material

I have posted an update [1] to the TTML2 ED [2] which populates the new
section on Implied Regions and which should allow closing out change
proposal 2 [3], which I also updated (see Resolution section).

[1] https://dvcs.w3.org/hg/ttml/rev/545ce48ed91b
[2]
https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml2/spec/ttml2.html#semantics-inline-regions
[3] https://www.w3.org/wiki/TTML/changeProposal002