Configuration enhancement

Kafka provides a lot of property configurable for both consumer and producer (See http://kafka.apache.org/documentation.html#consumerconfigs and http://kafka.apache.org/documentation.html#producerconfigs).
With this change, all this properties are exposed to the camel component.
To do that, i splitted the configuration in its own class so that it is possible to create a separated configuration that can be reused.