Improve indexing of literals used for categorization
A common case is that entries are categorized with skos:Concepts via dcterms:subject.
Hence, it should be possible to search for all entries categorized with a specific topic / concept.
Improved indexing of tag literals and resources
Proposed solution: split Solr-field tag into tag.literal and tag.uri. Move functionality from keyword and topic to tag.* and remove the fields keyword and topic.
Reopening the issue, the solution needs some discussion.