New duck prefabs, ai paths, and ai scripting

- Added new ducks as prefabs, one duck and three duck waves
- Added three new ai paths. Added ai paths to resources/prefabs folder
- Added first implementation of ai for game. Not completed, but idea is
for two duck waves to spawn every 15 seconds. If a duck wave is killed
off a new one will spawn. Ai paths will be instatiated once a wave is
created, deleted when wave is deleted.
(Once again ai script is not fully functioning, almost completed)