Use NFS on non-Windows systems, with related permissions changes

Based on https://gerrit.wikimedia.org/r/#/c/115114

Also, fix download link and document versions required, for NFS
specifically and in general.

Co-Author: Matthew Flaschen <mflaschen@wikimedia.org>
Change-Id: Ia9214dcd5fbbb6d8e3da417dd25a16bae3a50256