Split IoT into a separate ontology

[rjyounes]

Similar to gist accounting, gist fin, etc.

[rjyounes]

1. Deprecate now
2. Remove in next major release
3. Bring back in a gist IoT ontology

Bigger question: should these additional ontologies go in a different namespace? Then this is true deprecation/removal.

[rjyounes]

Duplicates #729, where we arrived at a somewhat different solution.

[rjyounes]

Forgot to actually close this.