[CREATE] OpenRaster: version numbering

[Andrew Chadwick]

It would be helpful if the specification had a version number, and if
the spec version number were written into ORA files:

  https://bugs.freedesktop.org/show_bug.cgi?id=37715
  https://bugs.freedesktop.org/show_bug.cgi?id=37717

Version numbers should be monotonically increasing w.r.t. time, and
easy to compare. For the purposes of the stack.xml schema, positive
canonical xsd:decimal values[1] might suffice here. Any thoughts?

We could version drafts too, provided that the constraints above are
kept. Embedded ISO date strings?


[1] http://www.w3.org/TR/xmlschema-2/#decimal

-- 
Andrew Chadwick