Core objects should keep their construction arguments
Break spaceship initialization in more methods

The position should not be acquired in this way. Later on, the map will
tell when should the ship be placed.
Update the documentation of Core::ParallaxBackground
Document Core's constants
Document Core::LoopingScene
Document Core::Map
Add the README and the LICENSE to the documentation
DRY, #dot is a #* alias
Document Core::Spaceship
Change the return type of the predicate methods to Boolean
Document Core::Bullet
Fix indentation
Revert #dot is not alias to #*
Update a bullet only if it is not dead
Document Core::BulletDispenser
Fix indentation