Start implementing priority A alerts for RFC 33

This implements the alerts:

• up (Reboot)
• reboot required (NeedsReboot)
• disk usage (DiskWillFillIn4Hours, DiskFull)
• RAID (RAIDDegraded)
• DRBD (DRBDDegraded)

Note that the alerts are labeled for the team TPA but that label value is as of yet not used for routing alerts.