Fix compatibility issue with java-manta 3.2.x and improve usability

Resolved the OSGi bundling conflict with log4j and added some general usability improvements.

you can get the same fingerprint from the private key that you get from the public key, asking users to pass in MANTA_PUBLIC_KEY is an unneeded burden
enhance the Dockerfile to accept a path to a cosbench-manta jar and leverage that in a local.sh script which can be used to iterate more quickly
introduce a build.sh to simplify creation of the docker container
introduce Dockerfile.alpine for a fewest-possible-layers alternative that's 40% smaller

Will publish joyent/cosbench-manta images to docker hub after we release 1.1.2.

TritonDataCenter / cosbench-manta