[frr] changing address-family vpn&encap config

[Lou Berger]

Hi all,

this is related to cleaning up the confusion of treating the vpn safi as
afi+safi, see https://github.com/freerangerouting/frr/issues/61.

Does anyone object to the following change to *config* in *stable/2.0* -
note this will break backwards compatibility (reading old will be
preserved, but output will only be new)

OLD

  address-family ipv4
  address-family ipv4 (unicast|multicast)
  address-family ipv6
  address-family ipv6 (unicast|multicast)
  address-family vpnv4
  address-family vpnv4 unicast
  address-family vpnv6
  address-family vpnv6 unicast
  address-family encap
  address-family encapv4
  address-family encapv6

new

  address-family <ipv4|ipv6> [<unicast|multicast|vpn|encap>] //default
is unicast

Lou