[Music] One song per gamestate, handle gamestate transitions

[chowdy]

• Song for the main menu
• At the start of the boot gamestate, start playing and looping the main menu song
• Song for play
• At the start of the play gamestate, stop any playing song and start playing and looping the play song
• Song for game over
• At the start of the gameover gamestate, stop any playing song and start playing and looping the game over song