medsrv/medcli: Remove prototypical medsrv web application and plugins

This was from a student project that has never been developed further.
And similar to the manager web application it lacks all sorts of modern
standards.  So just remove it and the two plugins it relied on.

The test scenario is renamed to avoid confusion (neither of the two
p2pnat scenarios uses medsrv/medcli).

testing/tests/p2pnat/different-nats/description.txt

@@ -0,0 +1,7 @@
+The peers <b>alice</b> and <b>bob</b> are hidden behind the NAT routers <b>moon</b> and <b>sun</b>,
+respectively. Due to this double-NAT situation they cannot set up an IPsec tunnel directly 
+but need the assistance from the mediation server <b>carol</b> with which they register under
+the pseudonyms <b>6cu1UTVw@medsrv.org</b> and <b>av9oEPMz@medsrv.org</b>, respectively,
+authenticating by means of individual pre-shared keys. Using the set of endpoints relayed 
+to them by the mediation server, the peers are able to set up a direct IPsec connection..
+In order to test the double NAT-ed IPsec tunnel both peers ping each other.