Minor tweaks to try and get bullets generating properly

- Make sure to add world as an observer to the controller to accept
attack input
- Have player start off with full ammo
- Fix bullet factory, make sure it knows of the world its generating
into
- Use cloning instead of copying to make code cleaner in bullet factory
- Add bullet image into loading
Switch to setting by FPS instead of period

- Also add a new value that's period in terms of secs for those who
prefer thinking in fractions of a sec instead of by milliseconds