* NACM recovery user session is now properly enforced. This means that if `CLICON_NACM_CREDENTIALS` is `except` (default), then a specific `CLICON_NACM_RECOVERY_USER` can make any edits and bypass NACM rules.
* If a default value is replaced by an actual value, RESTCONF return values have changed from `204 No Content` to `201 Created`
* clixon-config.yang: Removed default valude of CLICON_NACM_RECOVERY_USER
* Enforcing RFC 7950 Sec 7.6.1 means unassigned top-level leafs (or leafs under non-presence containers) are assigned default values.
* NACM default behaviour is read-only (empty configs are dead-lockedd)
* This applies if NACM is loaded and `CLICON_NACM_MODE` is `internal`
* Fixed: [default values don't show up in datastores #111](https://github.com/clicon/clixon/issues/111)
* Changed commit lock error tag from "lock denied" to "in-use".
* Changed unlock error message from "lock is already held" to #lock not active" or "lock held by other session".
* Fixed [lock candidate succeeded even though it is modified #110](https://github.com/clicon/clixon/issues/110)
* If-feature now supports and/or lists, such as: `if-feature "a and b"` and `if-feature "a or b or c"`. However, full if-feature-expr including `not` and nested boolean experessions is still not supported.
* Sanity check: if an `if-feature` statement exists, a corresponding `feature` statement must exists that declares that feature.
1. Added #ifdef extern "C" to public header files.
2. Changed variables that are key words in c++, to different names (like ns instead of namespace).
3. Changed char* to const char* for constant strings.
* In summary, a user registers an upgrade callback per module. The callback is called at startup if the module is added, has been removed or if the revision on file is different from the one in the system.
* The register function has removed `from` and `rev` parameters: `upgrade_callback_register(h, cb, namespace, arg)`
* The callback function has a new `op` parameter with possible values: `XML_FLAG_ADD`, `XML_FLAG_CHANGE` or `XML_FLAG_CHANGE`: `clicon_upgrade_cb(h, xn, ns, op, from, to, arg, cbret)`
* A generated clispec including state (default @datanodestate) also generated along with the config clispec tree (default @datanode)
* New mode `GT_HIDE` set by option `CLICON_CLI_GENMODEL_TYPE` to collapse non-presence containers that only contain a single list
* Added a prfix for cli_show_config/cli_show_auto so that it can produce parseable output
* Thanks dcornejo@netgate.com for trying it out and suggestions
