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.
Not a biggy, but it looks like you use __ prefix in a "this is very private member, don't dare touch it" meaning, where it is generally used to highlight class member. Just wondering if it is good practice, or should be avoided ? ( no need to change it here, as this convention seems widely used in the code )