0.3.5.6

BasicShooterEnemy:
- Removed Destroy() function so health can manage destruction of objects
Enemy:
- Added knockback distance field for projectile impact
- Added knockback method that applies a force to the enemy when hit by a
projectile
Health:
- Class to manage health of objects
Station:
- Added Destroy() method so the station has a way to be "destroyed"
- Later will be implemented as the player losing
Projectile:
- Added damage field
- Changed logic to destroy targets on impact, now just deals health
damage and lets the health class manage the rest