Use mv instead of cp&rm; Don't overwrite existing saves.

Hi there!

Here are two, in my option useful changes: First, should any game somehow mistreat symlink and re-create save directory, your script will move newly created stuff over old saves, most likely creating something unusable. With check [ -d "$NEW_DIR" ] in 5fe37bc this will not happen.

And second, d1fa097, using mv is faster than copying and removing, as average user has his $HOME only on one partition. And safer... Your original script may fail on cp and then happily rm old saves...