The problem that occurs when trying to reauthenticate with the Dropbox server was related with the no persistence of the new oauth token secret. Now and for both versions of oauth i'm always persisting the second value if there's one.
Using session cookie to identify the services the user is connected to. Improving the display of the resources service's name.
Removing unnecessary comments. Few code changes.
Using tags to split the user index template in code blocks.
Adding the necessary head tags for responsive features.
Resolving a compilation error when calling another template function: the parentheses were missing; Removing unnecessary style; Changed a Messages key; Changed the class of the sign out button.
Using localized messages.
Few more localized messages.
Created the visual components for the new play list features: save, load, clean, delete, shuffle playing and repeat play list.
Created the HTTP resources for the Playlist controller actions: save, load and delete.
Splitting code into new functions.