[TWILL-27] Upgrade to Kafka-0.8

Signed-off-by: Terence Yim <terence@continuuity.com>
[TWILL-27] Turn individual file log to TRACE level while building application bundler.

Signed-off-by: Terence Yim <terence@continuuity.com>
[TWILL-27] Make test less sensitive to machine run time speed.

Signed-off-by: Terence Yim <terence@continuuity.com>
Added KEYS file for release.
Alter version naming to fit incubator release requirement.