* Clarified semantics of main yang module:
* -y option to commands MUST specify filename
* CLICON_YANG_MODULE_MAIN MUST specify a module
* yang_parse() changed to take either filename or module name and revision.
* Removed clicon_dbspec_name[_set]().
* Use yang_main_module_name() instead.
* Replaced yang_spec_main with yang_spec_parse_module
* Added yang_spec_parse_file
* If you used old event callbacks API, you need to switch to the streams API
* See clixon_stream.[ch]
* Old streams API which needs to be removed include:
* clicon_log_register_callback()
* subscription_add() --> stream_register()
* backend_notify() and backend_notify_xml() - use stream_notify() instead
* Example uses "NETCONF" stream instead of "ROUTING"
* Added timeout option -t for clixon_netconf - quit after max time.
* That is, limited support of: ietf-yang-library.yang
* For example: `<module><name>example</name><revision/></module><module><name>ietf-restconf-monitoring</name><revision>2017-01-26</revision></module>...`
* Comply to RFC 8040 3.5.3.1 rule: api-identifier = [module-name ":"] identifier
* The "module-name" was a no-op before.
* This means that there was no difference between eg: GET /restconf/data/ietf-yang-library:modules-state and GET /restconf/data/XXXX:modules-state
* Previous support did no validation of values.
* Validation of types and CLI expansion
* Example extended with inclusion of iana-if-type RFC 7224 interface identities
* CLICON_NACM_MODE config option, default is disabled.
* Added username attribute to all rpc:s from frontend to backend
* Added NACM backend module in example
* Backend RPC register callback function (Netconf RPC or restconf operation POST) has been changed from: `backend_rpc_cb_register()` to `rpc_callback_register()`
* Backend RPC callback signature has been changed from: `int cb(clicon_handle h, cxobj *xe, struct client_entry *ce, cbuf *cbret, void *arg)` has been changed to : `int cb(clicon_handle h, cxobj *xe, struct client_entry *ce, cbuf *cbret, void *arg)`
* Frontend netconf and restconf plugins can register callbacks as well with same API as backends.
* Builds and installs a new restconf library: libclixon_restconf.so and clixon_restconf.h
* The restconf library can be included by a restconf plugin.
* Example code in example/Makefile.in and example/restconf_lib.c
* Authorization
* Example extended with authorization
* Test added with http basic authorization (test/test_auth.sh)
* Documentation in FAQ.md
* README.md extended with new yang, netconf, restconf, datastore, and auth sections.
