Remove ttp:version parameter attribute (#435).

[skynavga]

Closes #435.

[cconcolato]

why is this related to the version attribute?

[skynavga]

We had previously thought that tts:textShadow (a TTML2 feature) would replace tts:textOutline (a TTML1 feature). We now understand it isn't a replacement (driven by version) but both apply independently.

[cconcolato]

I don't see how this was driven by version and how this is related to ttp:version but I think the change is good. Approving

[cconcolato]

Built version at https://rawgit.com/w3c/ttml2/issue-0435-remove-version-parameter-build/index.html

[cconcolato]

@skynavga, just to make sure we have covered every aspect, I'm copying the results of your study of TTT and checking how this change affects them:

• [ttv] select between version specific default profiles
  This seems covered by the use of TTML2 profiles as the default given that it is a superset of TTML1.

• [ttv] select between TTML schemas associated with different specification versions (56 instances)
  Same as above. At some point, we had mentioned that a validator could choose the schema corresponding to the minimal profile that includes all required features. I think this is not needed for now.

• [ttv] contextualize length expressions in terms of version (in order to support new units) (2 instances)
  Can you clarify how this is handled?

• [ttv] enable deprecation warnings (1 instance)
  I think this is covered by the selection of a profile.

• [ttpe] select use of initial value of tts:position versus tts:origin (1 instance)
  We fixed this with Consider aligning initial values of tts:position and tts:origin. #551

• [ttx] select between tt element and region element for root of style inheritance (1 instance)
  This is covered by #546

• [ttx] select between version specific transformation helper class methods used during ISD transformation processing (24 instances)
  This seems internal to your software.

[skynavga]

@cconcolato thanks for checking my TTT study; there are a few things I need to add/tweak to cover these points

[nigelmegitt]

Great pull request, approving as is.

One question in my mind, possibly for a later change: should we also remove @version from isd:isd?

[skynavga]

@nigelmegitt I reviewed @version on ISD vocabulary, and decided it was appropriate there, since we don't profile the ISD vocabulary usage via features from which we might infer the ISD version.

[nigelmegitt]

@skynavga OK, I'm not sure about that but no objection from me to keep it in and moving on.