Fail early on severe Solr problems

[tokee]

If the SolrClient throws a org.apache.solr.client.solrj.SolrServerException: Server refused connection at: http://localhost:8983/solr/netarchivebuilder then warc-indexer should exit immediately with a proper return code. so that calling scripts can act accordingly.

Bonus: If Solr runs out of disk space, this is stated in another exception. There should be a similar early termination for that, with another return code.