Vertiv NETSURE DC rectifier shelf

I'm attaching a patch to add basic support for the Vertiv NetSure DC rectifier system.  This only includes support for the rectifiers - we do not have batteries connected on our systems so I'm unable to add/test battery related functionality.

• includes/definitions/mibs/vertiv.inc.php
  • Add new MIB.
• includes/definitions/os/vertiv.inc.php
  • Add new MIB (the basic information provided by this SNMP agent is pretty generic, and oddly, the enterprise ID in sysObjectID (8072) is different to the enterprise ID used to retrieve sensors values (6302)

New MIB file (NETSURE-NCU-MIB) for inclusion in mibs/vertiv is attached.

We're hoping this can be included in a future release so future updates don't break us