Moved block replacement to CreeperExplosion. Changed the CreeperComparator so the physics blocks are replaced after the solid ones, but before the dependent ones. Moved CreeperComparator to the blocks package.
Updated some TODOs.
If, for some reason, the protected blocks can't be replaced right away, drop them.
check_player_suffocate now returns the location where an entity should be teleported to safety, or its own location if it isn't suffocating. The teleporting itself is made in the calling method.