* Ensured you can add multiple callbacks for any RPC, including basic ones.

* Extra RPC:s will be called _after_ the basic ones.
  * One specific usecase is hook for `copy-config` (see [doc/ROADMAP.md] that can be implemented thus way.
* `rpc_callback_register` added a namespace parameter. Example:
   ```
     rpc_callback_register(h, empty_rpc, NULL, "urn:example:clixon", "empty");
   ```

lib/clixon/clixon_netconf_lib.h

@@ -68,5 +68,6 @@ int netconf_malformed_message(cbuf *cb, char *message);
 int netconf_malformed_message_xml(cxobj **xret, char *message);
 int netconf_trymerge(cxobj *x, yang_spec *yspec, cxobj **xret);
 int netconf_module_load(clicon_handle h);
+char *netconf_db_find(cxobj *xn, char *name);
 
 #endif /* _CLIXON_NETCONF_LIB_H */