explorer sort and search fixes

This PR addresses the following explorer issues:

Applies alphabetical sort for databases and person names in the metadata pane (resolves issue 40)
Allows users to load a single datasetid in URL (e.g., https://apps.neotomadb.org/explorer/?datasetid=1223)
Allows users to load multiple datasetids in URL (e.g., https://apps.neotomadb.org/explorer/?datasetids=1223,345,232)

This PR does not address issue preventing users to load sites in URL. Based on preliminary investigation, this fix may also require revising the related api endpoints. Further exploration is needed.

cc @SimonGoring @IceAgeEcologist

NeotomaDB / Explorer

explorer sort and search fixes #44