STORM-208: Add storm-kafka as an external module

This adds storm-kafka as an "external" module and incorporates it into the maven build.

This includes the commit history from the original storm-kafka from storm-contrib as well as the commit history from wurstmeister/storm-kafka-0.8-plus.

Aside from build incorporation, bump to kafka 0.8.1, and license headers, the only significant change is to add the topic name to the committed path.