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.
Can you check if we need this file at all? Perhaps it is needed anymore since all config files should be in the dist directory... perhaps it was for tests???