Migrate natpmp to offbynull/portmapper

[stokito]

It looks like the natpmp package uses jNAT-PMPlib library which is very old and seems abandoned.
But what it dangerous is that the package uses LGPLv3 License while the whole TomP2P uses Apache 2.
There is a newer https://github.com/offbynull/portmapper which also supports PCP (i.e. NATPMP 2) and even UPnP. It also uses Apache 2 License.
Could you please migrate to the newer library?