Include other graph projection patterns

In the OAK docs we describe some graph projection patterns implemented by different backends:

https://incatools.github.io/ontology-access-kit/guide/relationships-and-graphs.html#further-notes-on-owl-and-graph-projection

Many users of OAK want to be able to do things like navigate from "Illumina" to find things "manufactured by" Illumina. This is represented by HasValue restrictions. This is pattern is less common for the ontologies that are currently populated in Ubergraph, but if RG is to be used more widely then we need. A wider set is also provided by OBASK.

See:

- https://github.com/INCATools/ontology-access-kit/issues/809

The top level of the docs for RG say this is a tool for materializing existentials, so perhaps it is fine to focus on this. HasValue is outside the scope of what is supported in EL anyway (though it would be easy to have incomplete rules). But it would be good to link to some documentation that states this more explicitly.

See also

- #152
- #195
- #114

Start with the OAK documentation section on OWL and graph projection, then read issues #809, #152, #195, and #114 for the documented patterns and scope. Clarify which projection patterns relation-graph supports and update or link the documentation so the limits around HasValue and existential materialization are explicit.

Written by the indexing model from the issue text.