Change logic of applying facets. With a bit of extra configuration, search for datasets, including any of applied facets, not necessary all of them

To install ckanext-or-facet:

1. Install the ckanext-or_facet Python package:

   pip install ckanext-or-facet

2. Add or_facet to the ckan.plugins setting in CKAN config file

3. Starting from CKAN v2.10.4: Add ckan.search.solr_allowed_query_parsers = edismax bool to CKAN config file

# List of facets that are using OR when applied.
# (optional, default: empty list).
ckanext.or_facet.optional = tags res_format