Major update Space shield 1.5

The most of the final game is now implemented without major bug.
The last update is about :
- HighScore tracker
- Different behavior for each ennemy
- 6 different perks available each 30 kills, you can have, smaller hitbox for the core, bigger hitbox for the shield, faster shield, longer range for the shield, hp up and a last perks available when you reach 150 score : a 2nd shield at the opposite of the first one.

Someone gave me some good idea for new perks and ennemy to implement, so I will work on it, but this 1.5 version of the game is as I wanted it to be for the final game. 

I think that some design change can appear with particles and others things so this is not totally finished, stay tuned for the final version of the game.