Ontology URI --> ontology release and rendition

[kvistgaard]

The current ontology URI returns:

1. Version 3.1.0 -- consider synchronizing it so that the URI always brings the latest official release
2. An XML file -- consider using Turtle as the default browser rendition, which is more compact, easy to read and now used as the main publication format for most ontologies (although technical users can now get with this URI the file in TTL with cURL, having TTL in the browser will make it more accessible to a wider audience)