Add tests accessing Solr via SolrJ

While I'm thinking about testing, the code in BIGTOP-736 uses lower-level HTTP requests. Another viable way to access a Solr server is via the SolrJ Java API. This is actually fairly simple, the tricky bit will be getting the classpath correct. I'll attach a file that demonstrates a simple SolrJ test, which will fail miserably unless we resolve the classpath correctly.