Add feature to limit flag setting.

[jhooc77]

exemple part of flaggroups.yml

    1:
      setting: 'remove'
      editable: true
      flag: greeting
      editPermission: ""
      guidescription:
        - '&2Sets a message that will be'
        - '&2shown to players that enter'
        - '&2the region'
      applyto: []
      presetContents:
        0:
          setting: 'Hello! This is my land.'
          guidescription:
            - "setting greeting message to 'Hello! This is my land.'"
        1:
          setting: 'Hello! This is my house.'
          guidescription:
            - "setting greeting message to 'Hello! This is my house.'"
        2:
          setting: 'Hello! This is my test message.'
          permission: permission.test
          guidescription:
            - "setting greeting message to 'Hello! This is my test message.'"

It's a feature that limits the flag setting or can only be used by people having permission.
If you do not create presetContents or set it as an empty list, It can freely set it as before.