Add #should_render_field? support for all solr field types (index, show,
sort, search, facets).

Solr fields support :if and :unless configuration, e.g.

  config.add_index_field if: false
  config.add_index_field if: :some_helper_method
  config.add_index_field if: lambda { |solr_field, document| false }
  config.add_index_field unless: true
Add pt-BR translation

h/t Fabio Martinelli
Merge pull request #854 from projectblacklight/akretion-master

Add pt-BR translation
Merge pull request #853 from projectblacklight/if-unless

Add #should_render_field? support for all solr field types (index, show,
Add api documentation about return values of SolrHelper methods
Deprecation SolrHelper#get_single_doc_via_search
Deprecate SolrHelper#get_facet_pagination
Merge pull request #859 from projectblacklight/deprecate_get_facet_pagination

Deprecate SolrHelper#get_facet_pagination
Merge pull request #857 from projectblacklight/deprecate_single_doc

Deprecation SolrHelper#get_single_doc_via_search
Merge pull request #856 from projectblacklight/doc_solr_helper

Add api documentation about return values of SolrHelper methods
add SolrResponse#documents to translate solr response documents to a blacklight::solr::document model
Extract SolrDocument references from controllers and models and define
the solr document class to use in the blacklight configuration.

- add blacklight_config.solr_document_model configuration (defaults to
  SolrDocument)
- make Bookmarks polymorphic and refactor Bookmarks to use objects
  instead of passing IDs around