Deprecation and removal of RDF4J Solr sail

[hmottestad]

Solr is lagging quite far behind. They are stuck on an older version of jetty and an older version of lucene. They are planning to upgrade this in the next major version of Solr, but they also intend to remove the embedded solr support.

I propose we deprecate the Solr sail and remove it in the next major release.

Is anyone using the Solr sail, or know someone who is?

[nguyenm100]

2nd the rec. we found the implementation too brittle for production use.