Update mod setting and description enable the swarm

[veden]

Maybe a minor suggestion here, then, can you update the setting name and description a bit? The other setting, "Shrink nests and worms" is rather obvious what it's doing, whereas "Enable the swarm" made me think it was some kind of AI setting. Also, the description says "collision_mask", whereas I believe you should mean "collision_box"? I only pick on that distinction because collision_mask is an actual valid property, and that doesn't affect what I was looking for.