Figure out the real namespace if a document URI is given as namespace

Issue Summary

http://purl.org/ontology/bibo/ redirect to http://bibotools.googlecode.com/svn/bibo-ontology/tags/1.2/bibo.xml which is where the ontology is hosted. Some people might paste this document URI instead of the actual ontology namespace. The import process should look at the document and if possible figure out the ontology namespace, then either warn the user or use it directly. Thanks to Juergen for reminding of that.