added GO.xrefs file from https://raw.github.com/kltm/amigo/master/javascript/lib/amigo/data/xrefs.js into conf; source urls now constructed from this file (right now is static file, to be dynamic in future); augmented the xrefs file to contain additional sources including orphanet, hpo, clinvar; pubmed --> pmid; will revert to using neurolex wiki if the prefix is not defined in the xrefs file -- much work to do here.  #165
Merge branch 'master' of github.com:cmungall/monarch-app

Conflicts:
	lib/monarch/web/widgets.js