JOE closes SFTP connections

current situation

• JOE creates a new sftp connection for every "open Hotfolder by FTP" connection
• when closing a tab or JOE, the sftp connection is never released
  • many ssh processes on the remote server
  • many active ports on the remote server
  • many active ports on the local machine

desired behaviour

• JOE creates a new sftp connection for every "open Hotfolder by FTP" connection
• when closing a tab, all sftp connections for that tab are closed
• when terminating JOE, all sftp connections closed