add generic and improved NFS support with initial support for both FreeBSD and Linux

[VVelox]

Combines server and client stuff into one for NFS. Handles v3 and various v4 versions. Also provides info on mount points and what has mounted it.

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[VVelox]

Converting to draft. Was just converting a few systems to NFS4 and found that a few of those variables should be gauges.

[VVelox]

Did a bit more testing and made the mounted by for server stuff dependent on actually having info for it given it does not work with nfsv4 as there is no showmount -a equivalent.