Initial discovery and tests for FileEnumeration package

Not a request to merge yet... just opening this pull request for further discussions.  We just did a lot of that on Google Hangouts tonight where we decided that the code of the FileDifferentiation package needs to output List<String, List<File>> (input is the Map that is output by FileEnumeration).  This FileEnumeration code needs to be tweaked to permit input of a list of sources rather than just a single source (Path).  Oh, and FileManagement's copyPathname method will need an overload for taking a list of specific files/folders to copy (bypassing it's internal enumeration capability... which should probably be tweaked to use that provided by FileEnumeration package.  Lots to do :-)