This fixes a bug where shop owner accounts would not be created in certain cases e.g. when the owner had certain admin permissions or created the account for another player while having certain admin permissions.
Also add tax bypass permissions (#204, ChestShop.notax.buy/sell). When buying with that permission the buyer does not have to pay the tax (the seller will still get the reduced amount), when selling the seller will get the full amount instead of one lowered by the tax.
The permissions of the shop owner play no role due to there not being a good way of checking offline player permissions and it being a bit non-obvious for the buying/selling player if a shop would be with or without tax. This way all that gets changed is the amount the player pays/receives and not the shop owner (and the player should know their permissions/rank already)
The transfer event was necessary in order to correctly resolve who triggered the transaction. Economy adapters are now required to implement a listener for each of the events. It's also recommended that economy adapters that support transfers directly use that instead of passing it through subtract and add with the processTransfer method.
This changes events to store the database Account instead of an OfflinePlayer and deprecates any event method that uses/returns OfflinePlayer. This is necessary as Bukkit#getOfflinePlayer(String) queries Mojang for the UUID when the user was not found in the local cache. As we already store this information (name to UUID mapping) in our database we should not have no need to rely on querying Mojang. (This might make transactions fail for shop owners that haven't played before but that shouldn't really be an issue in most cases)
This should fix the issue where the player's short name on the shop sign does not reflect the actual player's name. This works by storing every uuid-username combination together with the associated short name and the last time the player logged in with that combination.
