This adds a button "down" to the playlist view, and works with both song-by-song basis and album basis (you need to click "down" for each item in the playlist however). This also sets the filename based on the file in the playlist under consideration.
This is adapted to recent changes in the API for the site. This also add a "all" button so you can download the complete playlist too (you need to clean the playlist then add the songs back for this to work).
This is based on previous work from Jixun Moe, but reworked to remove Chinese text, have the files saved with a real name (and not 1029138294283282.mp3), and support albums too.