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.
