BUG FIX : Projectile deletion

* when you were destroying a projectile due to it hitting an enemy
PLUS : Projectile damage depends on tower

* when selecting a tower to build, now also a certain damage is assigned
to that tower's projectiles from there on. 1 for machine gun and test,a
2 for siege and 20 for sharpshooter( maybe there will be stuff that
require more damage so sharpshooter will be great who knows)