integration with lucene/solr

[alimanfoo]

This issue is a placeholder for integration with Lucene text indexes, either via an index on the local file system or via a Solr server. This issue may need to be split in future as there are two possible implementations, one via pylucene, the other via pysolr.

See also #56.

[alimanfoo]

N.B., as integration with solr is via a network, some care would be needed to avoid memory bottlenecks when working with larger tables.