Remove Finished Queries from Grill Server memory 

Pull request which cleans up Finished query from Server memory and serves further requests from DB.

Major Changes in Patch:

* Introduced HSQL, dbutils &  dbpool dependencies for database related operations in grill server.
* Changed delay queue logic now to fire delay based on the size of the queue instead of time spent in the queue.
* Added Jackson (de)serializer for (de)serialization of column definition of result set metadata.
* Changed ResultSetMetaData class from Anonymous type to Named type in the Hive Driver. 
Will this change be required in all drivers?