Make destination_table not required

For flexibility, some users of HiveTriggeredHQLRunner might want to parametrize their query differently, like outputting to an hdfs path instead of a hive table. Removing destination_table from the required parameters and letting each DAG include what they need in extra_query_parameters will enable this. Renaming extra_query_parameters to hql_query_parameters seemed like a good idea, it sounds a lit less optional and makes it clearer where the parameters are interpolated.