Add "how to cite an ontology" info page

[mellybelly]

Discussed on operations meeting 2016.02.23

We agreed to add a new page with a citation policy and examples of how to cite some of our ontologies.

we can utilize the new data citation extension to JATS, see [https://peerj.com/articles/cs-1/]
for more info. Essentially this allows the citation of any identifier (so long as it meets standards as defined in the article) outside the paywall of the journal. This should probably be the version IRI but we should describe an example of what this should look like in a journal.

This can build on the text in the Open principle.

[jamesaoverton]

Added citation policy document with commit 49a8093