use batched Mutations available in Hector Mutator

Cassandra & Hector offer a lot of possibilities to batch mutations together.
This means Hector will not send data out to Cassandra until it receives the command to do so [execute()].
Really useful is this feature if you have to addOrUpdate two or more columns for one key (in one cf), it will then limit load on Cassandra, too.

A small prove of concept patch against 0.2 is attached.