Add Browse by Collection button to agrisufia homepage

[elrayle]

Sufia is oriented towards access to documents. It is not currently set up to navigate by collections. But there is work in the Hydra community that would allow Sufia to be navigated by collection. See the following note posted by Justin.

Hydra-collections version 5 has a basic collections show page (see http://sandbox.curationexperts.com/). Sufia uses hydra-collections, but I believe it's still using version 3 or 4. Once sufia is updated, you should only need to add the link to be able to list the collections.

-Justin

[elrayle]

See issue #25 for a bug preventing this from moving forward.

[elrayle]

On hold until after the Sufia sprint is completed. It may be address by the sprint.