fixed file separator for windows, diamond notation

Fixed file separation symbol to run cross-platform
Fixed diamond notation
Resolved unchecked warnings - all except one in FileTreeModel which I
suppressed as the cast is safe
Removed “FileSieve” label
Added minimum width for main frame
Changed DiffReport to indicate which files were marked for deletion.
GUI Fine Tuning

- Replaced file chooser to select destination for saving reports
- Included deleted files info in report
- Added scrolling to the bottom of the list on copy screen as files are
being copied
- Replaced text “copying …” to “creating …” per Jeff’s suggestion
- Added instructions about selecting multiple folders on select screen
Refactored variable as per the professor's comments.
Merge remote-tracking branches 'remotes/origin/BusinessLogicFineTuning' and 'remotes/origin/GUI-and-Persistence'
Merge branch 'GUI-and-Persistence' into Report-Update
Merge branch 'Report-Update' of https://github.com/JeffBlodgett/FileFilter into Report-Update
Merge remote-tracking branch 'origin/Report-Update'
Merge remote-tracking branch 'remotes/origin/master'
Merge pull request #22 from JeffBlodgett/Report-Update

Report update