xAPI Profiles 2.0 / Alignment to xAPI 2.0: Statement Template Rule values / comparison

[imartinezortiz]

Data Validation / Comparison based on new xAPIVersion property

• xAPIVersion added within xAPI Profiles 2.0 / Alignment to xAPI 2.0: Add xAPIVersion property to top level profile properties #274 to address xAPI Profiles 2.0 / Alignment to xAPI 2.0: Include xAPI Version in xapi profiles #267
• This PR addresses xAPI Profiles 2.0 / Alignment to xAPI 2.0: Statement Validation #268

This PR has been migrated and updated from FeLungs#11. See discussion there

[andyjohnson]

This profile will specifically follow xAPI 2.0. However, we don't want the xAPIProfile version to disregard previous profiles. New Profiles, profiles conformant to this standard, SHALL use xAPI 2.0 as the version. xAPI Profiles with the xAPIProfile version 1.X could be conformant to this standard, provided they only use properties from xAPI 1.0.X.

Profiles SHALL state the version in the xAPIProfile attribute. It SHALL be "2.0" or "1.X". Could have informative text describing that 2.0 is additive to 1.0.
Alternatively, New Profiles, profiles conformant to this standard, SHALL use xAPI 2.0 as the version. Profiles that use earlier xAPI versions (1.0 or later) MAY be conformant to this standard but only if they do not use contextAgents or contextGroups. Any xAPI Profile not using contextAgents or contextGroups within concepts, StatementTemplates, or patterns and is otherwise conformant to this standard, SHALL be considered conformant.