OAK-641: Improved benchmark tooling

Fix Jackrabbit 2.x setup code

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1453313 13f79535-47bb-0310-9956-ffa450edef68
OAK-676: Unify and upgrade SLF4j and Logback versions

Switch back to latest SLF4J 1.6.x version to avoid forcing OSGi changes

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1453314 13f79535-47bb-0310-9956-ffa450edef68