added functionality to use the CLI to disconnect peers
fixed DISCONNECT functionality


git-svn-id: https://gnunet.org/svn/gnunet@32815 140774ce-b5e7-0310-ab8b-a85725594a96
API header with disconnect call


git-svn-id: https://gnunet.org/svn/gnunet@32816 140774ce-b5e7-0310-ab8b-a85725594a96