luceneapi 6.x-2.0-beta4

NOTE: This release requires an upgrade of the Zend Framework components.

Bug fixes:
#628254: Memory leak in luceneapi_facet_counts_get()
#628178: array_keys() has slight performance penalty, remove where unnecessary
#628164: Facet and sort links are always "active" whether they are selected or not
#620340: Review best practices for translations, adhere to best practices regarding calls to t().
#628172: Fieldset facets don't display form elements
#626968: Error in bias query logic breaks some negative search queries
#614096: Several strings untranslatable
#620328: Remove l() function from translatable strings

New features:
#626974: Add hook_luceneapi_query_rebuild() to API
#619206: Add hook_luceneapi_sortable_fields_alter() to the API
#620460: Add API function to extract module and type from index object

API changes:
#620344: Remove second parameter from luceneapi_throw_error()