Create shortcuts to directories

[martinohanlon]

shortcut should be able to create shortcuts to directories as well as files.

The target directory would have to be passed as well formed paths (rather than having the option of using simple names like files to be searched).

Based on requests in #7 from @kiwi0fruit

[martinohanlon]

create_shortcut, create_menu_shortcut, create_desktop_shortcut should be changed to check to see if the target passed is a directory. If it is, a shortcut to the directory should be created.