* Fixed: Initialized session-id to 1 instead of 0 following ietf-netconf.yang

* Clearer debug levels `clicon_debug()`:
  1: Logical debug message
  2: Input and output packets
  3: Message dump in hex, xpath parse trees

lib/clixon/clixon_proto.h

@@ -54,7 +54,7 @@ enum format_enum{
 /* Protocol message header */
 struct clicon_msg {
     uint32_t    op_len;     /* length of whole message: body+header, network byte order. */
-    uint32_t    op_id;      /* session-id. network byte order. */
+    uint32_t    op_id;      /* session-id. network byte order. 1..max(u32), can be zero in client hello */
     char        op_body[0]; /* rest of message, actual data */
 };