Improve ordering of association sections on node pages

[sagehrke]

In #849, it was stated "The ordering of association on the page can be improved. Interactions is not useful and not in Monarch's core area. In contrast, diseases are. Put these before interactions"

[kevinschaper]

We use a yaml config on the backend to map association category names to string lablels, in the short term at least, we should just add a rank property to each of our association category definitions so that we can be sure that our core associations come up at the top.

Longer term, we probably want control over association sections to live in the frontend, especially as we find reasons to write specific code for our core sections.