Study available Solr enhancements

Some of the inner mechanics of Solr make it not quite perfect for the task of indexing RDF data, especially the way in which facets are generated could be a problem for this project (or at least for its working with facets). Therefore, existing enhancements to the program itself should be carefully reviewed and considered, keeping in mind that requiring the module's later users to download and set up yet another third-party program might not be a good solution.

Especially SIREn, once released, could be a vast assistance for this project.