Document expected arrangement of triple store that Ontobee code expects

[alanruttenberg]

The triple store, as I understand it, is arranged with a named graph for each ontology and all of its imports.

We need to document the conventions used for the naming of the graphs and any other specifics needed so that the SPARQL queries Ontobee uses will work, as setting the triple store up would be an essential piece of deploying another Ontobee installation.