beb9423 Improves loading offline player keys while fixing a few issues

• PlayerReceiveKeyEvent was not reflecting the correct amount added.
• Giving keys on player join event now respects the config options like "crate.keys.inventory-settings.give-virtual-keys" and "crate.keys.inventory-settings.send-message" which decide whether keys drop on the ground or not, or if a player should be notified if inventory is not empty.
• Baktus79 created a pull request which did fix an issue #930 as the first contribution, yet something hit me like truck-kun... and this is the result.