[Desktop] Open Playlists In Separate Windows

* iTunes let you open a playlist in a separate window; Spotify should too!

* You can have multiple playlists open at the same time.

* You could still have suggestions for song editions at the bottom of these playlist windows if the window is tall enough; if it's not then hide the suggestions. 

* You could use the same "song list table" that adjusts available columns based on width.