UDP mode for netcat (#72)

* Add UDP mode

* -c, -k and -K commands

Currently -c is broken for UDP

* Add new verbose debug messages for netcat

* Reimplemented -local flag

Author: N2D4

netcat/README.md

@@ -3,7 +3,15 @@ A SCION port of the netcat process.
 
 
 ## Usage
-```./netcat <host> <port>```
+```
+./netcat <host> <port>
+./netcat -l <port>
+```
+
+Remember to generate a TLS certificate first (this will generate them in the current working directory):
+```
+openssl req -newkey rsa:2048 -nodes -keyout ./key.pem -x509 -days 365 -out ./certificate.pem
+```
 
 See `./netcat -h` for more.