This commit adds support for configuring static PTMP overlays with VXLAN by
allowing to specify multiple IPs for »vxlan-peer-ips«. If more than one IP
is given ifupdown-ng will set up additional FDB entries for all peer IPs and
the Linux Kernel will do ingres / head-end replication for BUM traffic.
For a cleaner naming schema and simliar names to commercial vendor CLIs the
options to specify unicast or multicast peers have been renamed and aliases
added for compatibility to previous versions of ifupdown-ng:
* »vxlan-remote-ip« now is named »vxlan-peer-ips«
* »vxlan-remote-group« now is called »vxlan-peer-group«
Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>