chore: remove fireball duplicates and reference CombatSystem:fireBall

[jdrueckert]

I noticed that the projectiles are in fact mostly duplicates of CombatSystem:fireBall and only change the amount of damage as well as add a hurtingType that is not used anywhere.

I am aware, that this was done in preparation to create different types of staffs that can be used to enhance the LaS gameplay. However, most of the planned-for staff effects are unlikely to use "normal" projectiles in the first place. Also, LaS needs some work, before that kind of content logic additions can be taken up again.

So I vote for removing the duplicates and have the staffs simply reference CombatSystem:fireBall for the time being instead of duplicating the projectile prefab including the reference to the CombatSystem:ballSpell mesh that is extracted to engine in MovingBlocks/Terasology#5000