assets: fix bundle builder

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
search: configuration of facets per collection

* Adds FacetCollection model with db upgrade.

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
search: flask-admin module to configure facets

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>