Charging animation and more improvements

Animation added when the cannon is charging:

Also the bullet has been changed to match the charging animation, making it a sphere with a higher resolution and light blue colored.

The power up for increasing the projectile size has been removed. Since the Asteroids are big, the bigger shoot did not make much difference. Now there is more chance to optain the rest of the power ups which are more powerfull.

Projectile spawning spot has been changed where the animation of charging happens. Before it was spawning from the Cannon body.

Now the enemies will go in different directions. Before they were moving in a Stright line to the left side of the screen. Now they move to the left but with a lot more of variety of movement.

Now the enemies will move faster as the game level increases, making the game more challenging at higher levels.