Re-applied old patch from KAFKA-139

Had to make some additional changes based on further mainline work. Leaving
KafkaProject.scala in place as a reference for now.
Updated SBT JAR to 0.12.1
KAFKA-139 cross-compile multiple Scala versions and upgrade to SBT 0.12.1 patch by Derek Chen-Becker reviewed by Joe Stein
Merge branch '0.8' of https://git-wip-us.apache.org/repos/asf/kafka into 0.8