Added vault economy support. (optional)

You have to add a few extra lines in your language.yml and you can extend the info commands lines. (or you can regenerate the file)
Also you have to complete the config file with the following:
If you would like to use the new feature, you can setup each group for different inventory save pricing in the config file, for example.:
This also comes with a new permission: (If the player has this, then he/she won't have to play anything for the inventory save)

• invsaver.bypass.saveprice

Of course, if you have any idea how I could improve the plugin, I always welcome some feedback.