Add a CSV Output Writer

This CSV Output Writer can only be configured as an output writer in the JSON config file on a per-query basis because that is the coarsest granularity that can be guaranteed for everything to have the same epoch value. 

This is a cool output writer because it allows aggregate harvesting of all values from a given query, and outputs them with a header. The resulting CSV file can be imported into countless programs for further processing and analysis. 

The JavaDoc makes it pretty clear that this output writer cannot be configured on a global level. Also, it wouldn't make a whole lot of sense to aggregate data from multiple queries into the same CSV file anyway.