[Reviewer: Felix] Update bulk provisioning to handle new schema (fixes #30)

Felix, please can you review my changes to fix bulk provisioning following last week's schema changes?

I have
*   updated `bulk_create.py` to use `cassandra-cli` and fill in the new `public_ids` and `private_ids` tables
*   updated `ClearwaterBulkProvisioner.java` to fill in the new `public_ids` and `private_ids` tables
*   updated `README.md` to note that you need to call `sstableloader` for the two new tables
*   successfully live tested both bulk-provisioning approaches.