support drop database

Supports both

a. Drop database [restrict] - default mode is restrict
b. DROP database cascase

Drop database restrict expects that the database is empty and does not have any valid hive tables present when it is called else it fails on hive itself and the hook is not called in this case
In case of DROP database cascade , the hive server send information on the tables deleted and the database itself being deleted in the order mentioned . Hence drop database cascade generates a series of notification messages all expected to be executed in order to drop tables first and then the database