Put music everywhere

[FrancoisDuchene]

For now, musics are located in certains parts of the game; the main menu and the games. It would be better if we also put musics in the dialog parts and other parts of the game because it is relatively silent.
Now with how libgdx manage musics, one music is "prisoneer" of a class. Therefore, a globalmusic controller should be implemented to make sure musics are played correctly and not all at the same time.