Add support for logging output using Logback

This merge request adds:

+ Support for outputting metrics using Logback with time and size based roll over but without the file being renamed.  We had difficulties on Windows with the DailyKeyOutWriter and file renames.
+ Tidied up the code for KeyOutWriter and DailyKeyOutWriter to remove repeated code and shorten the methods.
+ Added the ability to set the delimiter from a setting as opposed to it being hardcoded to "\t".  Note it still defaults to "\t".