expose WebFinger link properties as remoteStorage.remote.properties

Rebase of #790
That wouldn't work I think because `this.userAddress` would be passed by value. Creating a function for every line of code is sillyIMO, then we'll end up with functions like `doIfConditionIsTrue` to wrap `if` :)

It should be clear how the code works from the function docs. I already added an extra inline comment in `src/dropbox.js` as well.