[Done for V0.41] Specific types for monster attractors

[Tonari]

If it comes to be able to select the kind of the monster that causes the effect of MONSTER ATTRACTOR (To the way of OBJECT_ACTIVATE), a specific monster can do original movement.

[George Gilbert]

This is done in V0.41 (the monster attractor has an optional extra parameter specifying a type of monster - if present then the attractor will only attract monsters of that type; if not it will attract any monster).