Better document behavior of SciGraph API when we have equivalent nodes

[cmungall]

We have a page on the wiki that describes our post-processing step for merging equivalent nodes, but we need to make the semantics more visible in the swagger itself, for casual API users.

For example, in the graph/neighbors/ path, it should say "this makes use of any equivalencies declared in the ontology [give example with a gene] [link to docs]"

Also it looks like the plain graph/id call does not use the equivalence?

[kshefchek]

Does the graph/neighbors/ work for non clique leaders? I think this has yet to be added: https://scigraph-ontology-dev.monarchinitiative.org/scigraph/graph/neighbors/Orphanet%3A353220?depth=1&blankNodes=false&relationshipType=subClassOf&direction=BOTH&entail=false
I think these are related: #203, #135