nifty-load-tester uses airlift/bootstrap, which brings in jcl-over-slf4j. Can't bring in both jcl-over-slf4j and commons-logging.
This change mainly adds control over number of boss and worker threads for the Netty channel factories used by the Netty client and server thread pools. It also renames NettyConfigBuilder to NettyServerConfigBuilder (to contrast with NettyClientConfigBuilder), and turns the config builders into actual builders (they were just used directly before).
Netty is configured by default to send its logging messages through JDK logging, but nifty-load-tester uses SLF4J