Begin work: new DO_term class
* begin work bringing in the new DO_term class
* removed hack with Disease stored in our search
* need to look at Gene page still
* #947
Disease DO_term
* fix schema to work on summary page
* use modelmap to map 'Disease' to 'DO_term'
* #947
Disease - changes from curator input
* make 'Disease Ontology Term' more obvious
* style dropdown to fit 'Disease Ontology Terms'
* change overview layout
* link to Disease ontology - update external links
* update search results to link to disease ontology
* fix #947