* 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
* These generated the Makefile variables: clixon_DBSPECDIR, clixon_SYSCONFDIR, clixon_LOCALSTATEDIR, clixon_LIBDIR, clixon_DATADIR which have been replaced by generic autoconf variables instead.
