use fulltext search in title and description.

* to quickly setup catalog_full_text table, you can use the following SQL.

  REPLACE INTO catalog_full_text SELECT uid, title, description FROM catalog;

* non fulltext queries like '=abc', '>abc', '%abc%' are supported.

* now erp5_full_text_mroonga_catalog is used for unit tests thus I recommend using it instead of erp5_full_text_myisam_catalog.

* to migrate existing MyISAM full_text table into Mroonga, you can use the following SQL.

  ALTER TABLE full_text DROP KEY SearchableText,
    ENGINE = mroonga,
    ADD FULLTEXT KEY SearchableText (`SearchableText`) COMMENT 'parser "TokenBigramSplitSymbolAlpha"';

* fulltext search score is no longer provided as (column_name) but now provided as (column_name)__score__.

* (category)_title, like source_title, related keys are automatically generated. (category)_description keys as well.