Moved launchMagicMissileExplosion to explosionEffect as it was only used by MagicMissile.
Added an explode function.
Cleaned up and somewhat reworked how MultiMagicMissile works. It now serves the purpose of a helper class for creating missiles (and store them) as it should have been.
Also merged m_canMove and m_exploded as it was basically the same thing (MagicMissile).