Adds the maxBackupIndex config option to the file appender

The current logging.yml template and setup don't allow an easy way to add the maxBackupIndex option.  Unfortunately if you add attributes to the node.elasticsearch.logging attribute they will be attached as es.logger.  While this is nice for logging options, there is no mechanism to add options to the log4j.appender .  This provides a fairly simple solution.

Ideally all of these options should be able to be dynamic.  I didn't want to create a massive overhaul to the cookbook and then have my pull request rejected.  

Hopefully this provides at least a simple way to rotate some logs.