Tajo 837: Register index meta information at Catalog

See the description in TAJO-837 (https://issues.apache.org/jira/browse/TAJO-837).
In this patch, I primarily focused on supporting register/unregister the index at Catalog.
In addition, some bugs are fixed.
It seems to abuse setQualifier() method because qualifier should be either ```[database name].[table name]``` or ```[table name]```. ```default`` may be a database name. 

Also, basically, we don't need to set manually qualifier for schema. Could you explain some reason why you manually set any qualifier?