All enemies now spawn on position.z

- Swarm enemies used to spawn on a different Z position [BUG]
- That issue is now resolved -- when spawn manager moves
enemySpawnPoint, it remains at position.z = 0, so match the player's Z
Can now set bullet prefs when spawning stationary enemy

- More control over bullet preferences when spawning stationary enemies:
speed, # of bullets, and delay
Cleaned up enemy names and prefabs