Changed collision detect method
Added asteroid collision detection
Fix asteroid collision detect and Changed Asteroid generation method
Add random sign method and changed random number generation.
Change ship rotation friction
Change asteroid generation method
Change ship acceleration method
Add Ship collision with asteroids, little change missile collision with
asteroids
Move life attribute to Entity class, add life counter to ship, remove
life attribute on missile
Add state attribute to World, add end condition to World, add exit
condition to GameScene, little changes on Ship related to access to some
attributes.

v0.2.0
Add utility method: getTexture for Picture class
logic about ship life and end game, add logic for max missiles on world.
Add GUI for Game Over state.
add logic for change GUI's and change game background.
Add Missiles Bar, fix paths to Missile Bar images.
Reposition Missile Bar on screen.
Add logic control ship life.
Add GUI for Ship Shield, changes paths to MissileBar images
Change key generation for files load with Media class.
Add UtilityGeom class