kafka-1799; ProducerConfig.METRIC_REPORTER_CLASSES_CONFIG doesn't work; patched by Manikumar Reddy; reviewed by Jun Rao
Added SSL for Kafka

Minor fixes, cleanup

Refactoring

Fixed tests compilation error.
Updated according to requested changes: refactoring, minor edits.
Added basic functionality for new producer.
bug fixes after rebase
bug fix after rebase
updated tests after rebase
changed default security to false
Got compile success with no errors after rebase, should check compile warnings
Changes to make broker backward compactibile with current producer and consumer