Extended cli_auto_show() with with-defaults argument, also changing its signature
Example: Added with-defaults argument to clispec
C-API: Added with-defaults argument to clicon_rpc_get_config
Replaced with-defaults prefix/namespace with constants
* Fixed: [Error message seen twice in some cases](https://github.com/clicon/clixon/issues/325)
* Extended `-l` command-line option to all clixon commands with a `none` option, eg `-l n` directs logging to `dev/null`
* Added ancestor config cache indicating wether the node or an ancestor is config false or true
* Improved yang cardinality lookup
* Added yang_init(), called from all apps using yang
NETCONF hello errors, such as wrong session-id, prefix, namespace terminates session
* Instead of returning an rpc-error reply
Changed YANG PATCH enabling:
* Now: `./configure --enable-yang-patch`
* Before: set YANG_PATCH constant in `include/clixon_custom.h`
Refactored Makefile for static linking
* 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)
- Fix event exit bug (set to new counter, dont increment)
- Changed default CI to be restconf=native instead of fcgi1~
- Tests:
- Change to same wait backend and restconf commands
- Change default restconf protocol from http to https
- Added autoconf config options, temporary for nghttp2 development: `--disable-evhtp`and `--enable-nghttp2`.
- Added special case for api-path:s beginning with //
* clixon_restconf daemon is installed in /usr/local/sbin (as clixon_backend), instead of /www-data
* `configure --with-wwwdir=<dir>` remains but only applies to fcgi socket and log
* New option `CLICON_RESTCONF_INSTALL_DIR` is set to where clixon_restconf is installed, with default `/usr/local/sbin/`
* Restconf drop privileges user is defined by `CLICON_RESTCONF_USER`
* `configure --with-wwwuser=<user>` is removed
* clixon_restconf drop of privileges is defined by `CLICON_RESTCONF_PRIVILEGES` option
* New clixon-restconf@2020-05-20.yang revision
* Added: restconf `log-destination`
* Several cases were not implemented fully according to RFC 7950
* Do not extend default values if when statements evaluate to false
* Do not allow edit-config of nodes if when statements evaluate to false (Sec 8.3.2)
* If a key leaf is defined in a grouping that is used in a list, the "uses" statement MUST NOT have a "when" statement. (See 7.21.5)
* See [yang uses's substatement when has no effect #218](https://github.com/clicon/clixon/issues/2$
