KAFKA-1668 Print an error if you try to alter a topic that doesn't exist.
kafka-1468; (followup) add back inadventently removed commit; patched by Guozhang Wang; reviewed by Jun Rao
kafka-1644; Inherit FetchResponse from RequestOrResponse; patched by Anton Karamanov; reviewed by Jun Rao
Merge remote-tracking branch 'origin/trunk' into testing