Maintain registry of DPs for different ontologies

## Ontology Patterns

Currently this ticket is the primary source for this registry. Note that some implementations are experimental, and may not fully conform yet. Where no DPs exist, instead we can cross-link github tickets.

Tick box when patterns are considered 'done'
- [ ] uberon https://github.com/obophenotype/uberon/tree/master/patterns @cmungall
- [ ] cl https://github.com/obophenotype/cell-ontology/issues/450
- [ ] to https://github.com/Planteome/plant-trait-ontology/tree/add-dp/patterns @marieALaporte
- [ ] agro https://github.com/AgriculturalSemantics/agro/issues/15 @marieALaporte
- [ ] plant stress and disease ontology https://github.com/austinmeier/ontology-of-plant-stress @austinmeier
- [ ] envo https://github.com/EnvironmentOntology/envo/tree/master/src/envo/patterns @pbuttigieg
- [ ] oba https://github.com/obophenotype/bio-attribute-ontology/tree/master/src/ontology/patterns @cmungall
- [ ] hpo https://github.com/obophenotype/human-phenotype-ontology/tree/master/src/patterns @drseb
- [ ] go https://github.com/geneontology/design_patterns @dosumis
- [ ] ecto (note this is different from ENVO...) https://github.com/cmungall/environmental-conditions/tree/master/src/patterns @cmungall and @balhoff

Start with the checklist in issue #22 and inspect the linked ontology repositories and tickets for existing design patterns. Mark entries done only when the referenced patterns are considered complete; otherwise add or preserve a cross-link to the relevant ticket.

Written by the indexing model from the issue text.