Swapped set to get when dealing with ObservableList<File>. Now creates
the two ObsevableList<File> itself, instead of relying on a set-method.
Removed unused import.
Sets file name instead of file path as text.
Uses FileNameCell on leftList, and checks if resources is null before
setting internationalized strings.
No significant changes.
Added sorting, adding and clearing, and added functionality to the new
gui.
Created a new class to hold a delay and BufferedImage. To be used in the
generator for variable frame delays.