String has to be surrounded by quotes
prevent overwrite of event host field
Closes #1668
Dynamic include_keys and exclude_keys for kv filter
Closes #1618
Change credentials default to [], use empty array

closes /elasticsearch/logstash/#1619
Removed nil check
Closes #1661
Merge @joekiller's Kafka plugin to logstash-core
Add documentation and tests
Use scala version 2.9.2 and Kafka 0.8.1.1
Closes #1472