Reworked collisions

It's now possible to check against collisions with each Entity of a given name by using the global functions:

• CollisionFound(dx, dy, entity, colliderName)
• CollisionBoxFound(x, y, width, height, entity, colliderName)
• CollisionPointFound(x, y, entity, colliderName)

I've also added a small starting example you can use as a base for your projects in the Game.lua file