Move out the session initialization in the mpris-scrobbler daemon.

[mariusor]

Since the second step of the API authentication does not require the user's intervention, I want to switch from using the signon binary for loading the session_key.

This would mean that once we load the token successfully, we send a signal to the daemon, which calls the API to initiate the session.

I need to research this a bit more as there needs to be a wait time before asking for a session, to make sure the user approved the applications' token.