Completed task #625498. Added text to description on how to hide the block when no reommendations are returned.

Changed _luceneapi_morelikethis_block_view() to luceneapi_morelikethis_block_view() so it could be public.  No need to make it private.

Changed admin settings page tp a menu local task of luceneapi_node, added check to make sure Search Lucene API 2.0 is installed.

Changed luceneapi_morelikethis_get_nid() to luceneapi_morelikethis_nid_get(), added priority queue caching.