Merge pull request #1 from JeffBlodgett/LogicInterfaces

Initial interfaces for business logic
Merge pull request #3 from JeffBlodgett/LogicInterfaces

interface renames
added empty .gitignore to ./src/test/java/FileSieve/ folder so ANT will see that (currently empty) folder and compile successfully
Added interfaces for UserPreferences to save selected options and window position information and for DiffReport to output a report to a file.