Standardize the major worker interfaces

DocumentMaker, SolrIndexService become analogous to LinkedDataService and DiscoveryWorker.
First cut at a Solr schema.

Copy the one from LinkedDataIndexer and modify it to work with the current Solr.
Test all phases outside of Hadoop.

Discover URIs, expand their LOD, build Solr documents, and add to the index.
Fix unit test to conform to package renaming.