Fixed definitions.

Fixes #2526

Some last minute simplifications after it was pointed out we
had relevant existing vocabulary.

…ge bug.

* Create issue-2543.rdfa

adds coverage for non-profit organizations

* Create issue-2543-examples.txt

adds coverage for non-profit organizations

* Update issue-2543.rdfa

* Update issue-2543.rdfa

Add NL non-profit types to NonprofitType enum list

…nd citizenship requirements (#2492)

also rewording 'vendor' as 'merchant' for readibility

This file got dropped accidentally during the fast-tracking of
COVID-changes last month. See github issue for history; originally
modeled with a single property but using two now to better capture
the semantics of EIDR.

* Adding properties for teaches and assesses to CreativeWork and EducationEvent; extending range of educationLevel, adding guidance to educationalAlignment, amending examples.

* referencing issue 2427

* referencing learning outcomes in defitions to fulfil requirement of #2432