Added support for list x y;
Uses a mechanism to parse as unknown XML body and post-parsing replace with list keys
Fixed example and test to work with new TEXT syntax
* Stricter checking of outgoing RPC replies from server
* See [RPC output not verified by yang](https://github.com/clicon/clixon/issues/283)
* This lead to some corrections of RPC replies in system code
* Made NETCONF message handling more strict according to RFC 6241
* Set `CLICON_NETCONF_MESSAGE_ID_OPTIONAL` to true to accept omission of message-id attribute
* Fixed: [need make sure message-id exist in rpc validate #240](https://github.com/clicon/clixon/issues/240)
* This means that files and datastores supporting modstate also looks for deleted or updated yang modules.
* A stricter binding which gives error if loading outdated YANG file does not exist.
* Stricter yang checks: you cannot do get-config on datastores that have obsolete YANG
* Added xerr output parameter to `xmldb_get0()`
* Hello message semantics has been made stricter according to RFC 6241 Sec 8.1, for example:
* A client MUST send a <hello> element.
* Each peer MUST send at least the base NETCONF capability, "urn:ietf:params:netconf:base:1.1" (or 1.0 for RFC 4741)
* The netconf client will terminate (close the socket) if the client does not comply
* You can set `CLICON_NETCONF_HELLO_OPTIONAL` to true to use the old behavior of essentially ignoring hellos.
* New clixon-config@2020-03-08.yang revision
* Added: `CLICON_NETCONF_HELLO_OPTIONAL`
* The base capability has been changed to "urn:ietf:params:netconf:base:1.1" following RFC6241.
* Removed xml-stats non-config data (replaced by rpc `stats` in clixon-lib.yang)
* Added option `CLICON_YANG_UNKNOWN_ANYDATA` to treat unknown XML (wrt YANG) as anydata.
