FLUME-2455. Kafka Sink Documentation.

(Thilina Buddika, Gwen Shapira via Hari)
FLUME-2470. Kafka Sink and Source must use camel case for all configs.

(Gwen Shapira via Hari)
FLUME-2470. Kafka Sink and Source config updates. Missed a couple files in the last commit, adding them.

(Gwen Shapira via Hari)