Sri | Implemented 2 level partitioning scheme for events.

Partitioning and maintaining events table on brands and year/month.
Partitions are only created for brand-year-month combinations that have data.
Partitions are automatically created when they don't exist (month rollovers for example)
The 2 level scheme is structured to be more logically representative of the scheme (no technical reason why all partitions cannot be direct children of events)