Assign cost per-node rather than per-package

[justisr]

I was trying to implement your plugin here: https://github.com/justisr/Broker-Spigot/tree/master/src/main/java/com/gmail/justisroot/broker/defaults/permission
But it seems your plugin ties costs to groups of permissions rather than individual permissions, which makes determining the price that a user should pay for a single permission impossible.

I would ask and also recommend that you consider determining perk costs based on the total cost of all permissions included in the package. This works best for all users of your plugin regardless, because there are many reasons why a buyer of a perk might already have one or more of the permissions included in the package, and it wouldn’t make sense to charge them the full amount. Assigning cost per-node would enable more packaging options to server owners as well, since they could include the same permission across multiple different related packages, and know that if someone buys one package, the cost of the others which included a shared permission will reduce proportionately.