luceneapi 6.x-1.3

Bug fixes:

- Added fix to prevent orphaned nodes from remaining in the index. The results showed "Page not found" titles.

- Fixed unclosed bold tag in the Search Lucene Content administration page.

Minor changes:

- Prefixed columns with table names in _luceneapi_node_rewrite_sql() to prevent name clashes.

- Fixed the misnamed title of the "Clear cache" page.

- Added safeguards to prevent the site from throwing fatal errors if the ZF components become unavailable.