Add predicate offers - fixes #528

[stevenchalem]

Closes #528.

Added predicate gist:isOfferOf, and changed the formal definition of gist:Offer to refer to the new predicate instead of gist:hasDirectPart

[Jamie-SA]

The prefLabel needs to be fixed, and a possible suggestion for the release notes.

[uscholdm]

Change prefLabel per Jamie's suggestion.
Update release notes per my suggestion

[rjyounes]

We've agreed to change from isOfferOf to offers. Maybe add scopeNote/example about the different uses (with Offer vs Organization/Person etc).

Need to generalize the definition.

[rjyounes]

DECISION:

skos:definition "Relates something to a thing it makes available for acceptance or rejection." ;
skos:example "An instance of gist:Offer offers a specific product at a particular price; a company offers an employee benefit; Honda offers vehicles for sale.";

[uscholdm]

@stevenchalem

skos:definition "Relates something to a thing it makes available for acceptance or rejection."

I suggest:

• skos:definition "Relates something to a thing that is being made available for acceptance or rejection."

[uscholdm]

A couple of rewording suggestions.

[rjyounes]

@stevenchalem Sorry about the back and forth. Michael is willing to go ahead with offers and I trust his judgment on this. So let's go ahead and finalize this PR. Thanks.

All requests have been addressed.