Integrate remoteStorage

[pthulin]

• Allow users to sign in via it.
• Allow users to store playlists on it.

[jancborchardt]

And people should also be allowed to store friends, follows and playlist subscriptions with it. This is already done similarly by Shared Stuff.

Also, cc @michielbdejong :)

[michielbdejong]

Hi! FWIW, we now consider version 0.7.0 of remoteStorage.js to be in 'developer preview', which basically means that people should stop developing for 0.6.x, and start developing for 0.7.x. See https://github.com/unhosted/remoteStorage.js/tree/v0.7 for more info on how that works, and we would love to have your feedback on the examples of how the remoteStorage.* modules work! (see the 'example' directory)