Feature/solr integration

Implementation of Solr indexing of Articles and feeds has been finalized;

solr server has been configured to conform the needs of this branch. Articles and feeds are indexed in separate cores to facilitate search.
A script for initial loading of existing article and feed collections was added.
Minor improvements in the rss scraping code were also introduced in this PR

Documentation on how to configure the Solr server was added to the project's README.md