/cluster/…/backup

Cmdlets for /cluster/backup and below. 6 cmdlets.

• Get-PveClusterBackup: GET /cluster/backup
  List vzdump backup schedule.
• New-PveClusterBackup: POST /cluster/backup
  Create new vzdump backup job.
• Remove-PveClusterBackup: DELETE /cluster/backup/{id}
  Delete vzdump backup job definition.
• Get-PveClusterBackupIdx: GET /cluster/backup/{id}
  Read vzdump backup job definition.
• Set-PveClusterBackup: PUT /cluster/backup/{id}
  Update vzdump backup job definition.
• Get-PveClusterBackupIncludedVolumes: GET /cluster/backup/{id}/included_volumes
  Returns included guests and the backup status of their disks.