Add Enemy Ship model and dependencies
Add Rigidbody to Enemy
Add Sphere Collider to Enemy
Add generic EnemyController.cs script
Make Enemy avoid Asteroids using collider
Refactor Player explosion from Asteroid to Player
Add explosion prefab and dependencies to Enemy
Add sound to enemy explosion prefab
Make Enemy follow Player
Make Enemy stop following Player if too near
Add initial Priximity Detector to Enemy
Make Enemy use ProximitySensor for obstacle avoidance
Give enemy gun, audio, fx, turn it into prefab
Remove remains of Unarmed tag in DestroyByContact.cs
Only score Player's kills
Fix Enemy prefabs following Player
Make Enemy tilt in the right direction
Stop Enemies recoiling from own shots
Inc. Enemy chance to 0.3; reduce jerkiness with Interpolation
Improve Enemy GameObject

* Shoot to target detected with ProximityDetector
* Ignore own shots and other Enemy ships
* Increase delay after spawning an Enemy to prevent Asteroid crashes
* Refactor