Pre- and Post- Backup Commands

[tobischulz]

Each SourceServer can have an Array of pre_backup_commands and post_backup_commands that will called via SSH on every backup run. As the names says, before the backup starts and after it has been completed successfully.

On Database there are already two columns to persist the arrays of commands.

• pre_backup_commands
• post_backup_commands

Add two new Jobs that will handle this.