CLC-3322 Research Hub revisions for consistency

https://jira.ets.berkeley.edu/jira/browse/CLC-3322

Revisions to make Research Hub more consistent with other proxies. I inlined the business logic from the Research model object into the ResearchUserProxy, and added smart caching of the processed JSON at the proxy level. I also changed the username property in settings from "test_user" to "username". 

There are still some TODOs in ResearchUserProxy. It should use Httparty instead of open-uri for its connectivity (that's CLC-3385), and it should have rspec coverage of the error states (after CLC-3385 is done, that will be easier to do).