Add config option for commands to run when backup starts and ends

[espidev]

Add a config option to run commands when the backup starts and when it ends.

[CloudeLecaw]

definaty a nice idea.

So itwould be possible to inform admins and staff ingame too with a designed message when a backup starts and when it ende.

Well may same can be done for the uploading start and end of a backup when ftp or sftp upload after creation is used