Add support for `owl:Thing` and `owl:Nothing`

[NicolasRouquette]

User Story

As an ontology author, I would like to refer to owl:Thing or owl:Nothing in OML so that I can express relations whose domain or range are one of these classes or force a class to be empty by specialization of owl:Nothing..

Detailed Description

Description providing additional details and context.

Proposal:

In the OML vocabulary for <http://www.w3.org/2002/07/owl>, add two aspects for Thing and Nothing.

Acceptance Criteria

• [ ] Given [Condition], then [Expected Result]
• [ ] Given [Condition], then [Expected Result]
• [ ] Given [Condition], then [Expected Result]

Sub-task List

• [ ] Task 1
• [ ] Task 2
• [ ] Task 3

[StevenJenkinsJPL]

I don't think we should refer directly to OWL entities in OML. These concepts (universal and empty sets) belong to set theory; OWL just has its particular names for them. OML should have them too, but not by OWL's names. We should have our own, either Universal and Empty or Thing and Nothing. They will be mapped to their analogues in the OML-to-OWL transformation.

[melaasar]

Added owl:Thing and owl:Nothing to the owl ontology https://github.com/opencaesar/core-vocabularies/blob/159faeca9f10a7078b5efa08ef79b526f980d38a/src/oml/www.w3.org/2002/07/owl.oml#L33-L35