move Sound property to new Entity subclass. change create method for
Entity. change constructor for GroupController and its subclasses.
rename World to BaseWorld
Refactor GroupController
change states Management. rename classes for group controllers. refactor
ScoreBonification.
add focus property to BaseWorld
set State for Missile. change missile creation. rename method on
GeomUtil.
change act method for SingleWorld. change run, pause methods for
SingleWorld. add resume method to BaseWorld. Fix errors on restart game.