Render "GW: Electronic Book" in search results as link to resource

[kerchner]

As per discussion of @adityadharne and @cummingsm . This can be done together with gwu-libraries/obento#174 as it will entail enhancing the launchpad search API to add a single electronic resource link when appropriate.

@cummingsm please feel free to assign this to a launchpad milestone (or not)