Default stabilizer config should use rolling file appender for worker

Changed default Log4j appender to RollingFileAppender. Default values are 1gb per file and 5 backup files (which creates 6 gb of log data in 6 files at maximum). The Log4j configuration file can be overwritten by a local file in the working directory.

This resolves issue #363.
No, it's a temporary file like the other XML files you can override (Hazelcast config, Hazelcast client config etc.). I could move the directory to the worker home if you want to.