Split pick-photos out from sort-photos

And created tests
Use trash-cli if it's installed
pick: Added [-f|--favorites-dir] option for setting aside favorite photos.
pick: pause to review unselected photos
pick: Don't review videos when only picking favorites
pick: Added [-n|--no-delete-src] argument
test: Remove unnecessary code
import: Added [-n|--no-delete-src] argument
sort: Preserve file modified time