* For backward compatibility, load of startup and running set CLICON_XML_NS_STRICT to false temporarily.
* Added three-valued return values for several validate functions where -1 is fatal error, 0 is validation failed and 1 is validation OK.
* This includes: `xmldb_put`, `xml_yang_validate_all`, `xml_yang_validate_add`, `xml_yang_validate_rpc`, `api_path2xml`, `api_path2xpath`
* Added new xml functions for specific types: `xml_child_nr_notype`, `xml_child_nr_notype`, `xml_child_i_type`, `xml_find_type`.
* For Example, adding bad-, missing-, or unknown-element error messages, etc instead of operation-failed
* Removed delete-config support for candidate db since it is not supported in RFC6241.
* Switched the order of `error-type` and `error-tag` in all netconf and restconf error messages to comply to RFC order.
* Added example_rpc RPC to example backend
* Renamed xml_namespace[_set]() to xml_prefix[_set]()
* Some restconf error messages contained "rpc-reply" or "rpc-error" which have now been removed.
* Netconf/Restconf RPC extra input arguments are ignored (https://github.com/clicon/clixon/issues/47)
* NACM module support (RFC8341 A1+A2)
* Recovery user "_nacm_recovery" added.
* Example use is restconf PUT when NACM edit-config is permitted, then automatic commit and discard are permitted using recovery user.
* Example user changed adm1 to andy to comply with RFC8341 example
* Yang code upgrade (RFC7950)
* RPC method input parameters validated
* see https://github.com/clicon/clixon/issues/4
* Correct XML namespace handling
* XML multiple modules was based on "loose" semantics so that yang modules were found by iterating thorugh namespaces until a match was made. This did not adhere to proper [XML namespace handling](https://www.w3.org/TR/2009/REC-xml-names-20091208), and causes problems with overlapping names and false positives. Below see XML accepted (but wrong), and correct namespace declaration:
```
<rpc><my-own-method></rpc> # Wrong but accepted
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> # Correct
<my-own-method xmlns="http://example.net/me/my-own/1.0">
</rpc>
```
* To keep old loose semantics set config option CLICON_XML_NS_ITERATE (true by default)
* XML to JSON translator support for mapping xmlns attribute to module name prefix.
* Default namespace is still "urn:ietf:params:xml:ns:netconf:base:1.0"
* See https://github.com/clicon/clixon/issues/49
* Changed all make tags --> make TAGS
* Keyvalue datastore removed (it has been disabled since 3.3.3)
* debug rpc added in example application (should be in clixon-config).
* Improved unknown handling
* Configure option `CLICON_YANG_DIR` is changed from a single directory to a path of directories
* Note CLIXON_DATADIR (=/usr/local/share/clixon) need to be in the list
* 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
