Changing control buttons into images instead of css buttons, adding logo, and making newSong global

* New images are all self-explanatory
* newSong is now global because can't check if a user has been in a song (for removing him from a channel when disconnected) unless a song has already been created when he logs in.  And users are going to create songs after logging in - there's no point in going to the site otherwise
* newSong is now definined at the same time newUser is