Implement consistent logging for setters in me.prettyprint.cassandra.model.ConfigurableConsistencyLevel

[lewismc]

In the above class, we make the slf4j imports and only use them once [0]. To save one having to use their own logging it would be nice for Hector to log at INFO for ConfigurableConsistencyLevel.

This should be trivial to implement.

[0] https://github.com/hector-client/hector/blob/master/core/src/main/java/me/prettyprint/cassandra/model/ConfigurableConsistencyLevel.java#L49