riotctrl_shell.gnrc: add doctests as parsing examples
riotctrl_shell.gnrc: add doctests as parsing examples

OlegHahm/RIOT,authmillenon/RIOT,jasonatran/RIOT,ant9000/RIOT,jasonatran/RIOT,jasonatran/RIOT,ant9000/RIOT,OTAkeys/RIOT,OlegHahm/RIOT,ant9000/RIOT,OlegHahm/RIOT,ant9000/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,kYc0o/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,miri64/RIOT,OlegHahm/RIOT,miri64/RIOT,RIOT-OS/RIOT,miri64/RIOT,RIOT-OS/RIOT,OTAkeys/RIOT,ant9000/RIOT,kaspar030/RIOT,authmillenon/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,kaspar030/RIOT,jasonatran/RIOT,miri64/RIOT,miri64/RIOT,kYc0o/RIOT,OlegHahm/RIOT,kYc0o/RIOT,kYc0o/RIOT,kaspar030/RIOT,OTAkeys/RIOT,jasonatran/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,kYc0o/RIOT,authmillenon/RIOT