Add in ability to filter by role model identity

[KirstieJane]

At the moment we're just searching across all of the information in the database for each role model, it would be preferable if we could actually filter the results explicitly by the role_models variable in the data sheet.

I'm not sure how to do it....but I be some smart cookie out there does 😄

I think the place to make the changes will be js/app.js and ultimately we'd need to integrate it into the site/search_database.html file.

Let me know if there's anything I can help with!