For 27137 - Set additional fields to ignore when comparing file versions

This adds a configuration setting that can be used to specify additional fields to ignore in file paths when comparing them to find differing versions of the same file.  

For example, if the file name contains the user initials but all users should see these files as a continuous sequence of versions then this setting can be used to achieve this.
It's not entirely hidden - the templates in the configuration require a version field to exist.  It would actually be a lot harder to validate if the version field were allowed to be more arbitrary...  It's definitely one we should talk about though