Add option to make attacks roll-over

[MilesBHuff]

In the original Golden Sun games (and this engine, at present), queueing an attack for an enemy that dies before the attack is executed, results in the attacker guarding.

In Dark Dawn, the attacker automatically picks a new target. I'm not sure if this new target is random or merely the closest to the dead target.

There are virtues to both systems. Some players or map-creators may prefer one or the other.

[jjppof]

Will label it as a next release feature, but we can check it with Mac (teawater) at discord. He knows everything about GS mechanics. If it's something simple, we can consider adding it to the first release.