wireguard: initial implementation of wireguard protocol

wireguard: initial implementation of wireguard protocol

Type: feature

The main information about plugin you can see in README.md

vpp# wireguard ?
  wireguard create                         wireguard create listen-port <port> private-key <key> src <IP> [generate-key]
  wireguard delete                         wireguard delete <interface>
  wireguard peer add                       wireguard peer add <wg_int> public-key <pub_key_other>endpoint <ip4_dst> allowed-ip <prefix>dst-port [port_dst] persistent-keepalive [keepalive_interval]
  wireguard peer remove                    wireguard peer remove <index>

Change-Id: I85eb0bfc033ccfb2045696398d8a108b1c64b8d9
Signed-off-by: Artem Glazychev <artem.glazychev@xored.com>
Signed-off-by: Damjan Marion <damarion@cisco.com>
Signed-off-by: Jim Thompson <jim@netgate.com>
Signed-off-by: Neale Ranns <nranns@cisco.com>
Signed-off-by: Damjan Marion <damarion@cisco.com>