MFp4: @179066

Add page which describes VNET network stack virtualization infrastructure.

Submitted by: bz
Sponsored by: The FreeBSD Foundation
Sponsored by: CK Software GmbH


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274745 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f