Added health bar.
Move all bullet-related functions into one place

Rather than cluttering up main, we are moving all the bullets into
one place, and requiring it.
Use : instead of . to pass self into metatable
Bullet is being updated and drawn and collided

A lot of refactoring and rearrangement

I have passed in necessary information like playerCoords and got
the bullet firing, colliding with objects, but need to test whether
it can hit other players. I was however able to hit myself, so it
must be working.

Remove unused Sprite

Though it might make sense to create Gamelost.Sprite.Bullet and Gamelost.Sprite.Player?

Rename sprite to sprites

More cleanup