At the end of this task the bigtable::Table class will have a member function to apply multiple mutations to multiple rows in a single call. A good name might be BulkApply(), but Apply() overloaded for some class that encapsulates multiple mutations is also acceptable.

The function should follow the same policies defined in #12 to control what operations are idempotent, how to backoff when retrying RPC operations, which error codes are retryable, etc.