Spike: investigate options for format icon sets

[tclayton33]

One recommendation that came out of the usability study was to consider implementing an icon set for resource type that could be displayed alongside the resource type facets and the records in the results list. For example, Stanford's Searchworks and UPenn's Franklin use these in both the facets and the search results. Cornell uses them in search results. Please explore our options for available icon sets (ideally free and easy to implement).