added message counters to KafkaSinkV2
Changed counters from ints to longs to prevent overflow
updated sample KafkaSinkV2 config, added 2 new sink stats, fixed pending message count
clarified retry/failure logic
added comment explaining thread pool issue in KafkaSinkV2
Simplified failure/retry logic
Merge pull request #143 from BrightTag/master

Added better counters to surosinkstat for KafkaSinkV2