New `grouping-treeref` option added to clixon-autocli.yang
Default is disabled, set to true to generate smaller memory footprint of clixon_cl
Add prefix "mtpoint:" to cli api-paths to identify change of yang schemas
* RFC 8528 yang schema mount-points:
* Made expand_dbvar and cli_dbxml mountpoint-aware (RFC 8528)
* autocli supportgenerate
* Made api_path2xml and xml2api_path mount-point-aware
* Temporar fix in clixon_custom.h: XPATH_CANONICAL_SKIP_CHECK
* `xml2xpath()`: Added `apostrophe` as 4th parameter, default 0
* removed extra assert.h includes
* Internal NETCONF (client <-> backend)
* Ensure message-id increments
* Separated rpc from notification socket in same session
* Removed coverage icon from homepage since it stopped working some time ago
* Added flag names: `CLIXON_DBG_*`
* Added maskable flags that can be combined when debugging:
* `DEFAULT` = 1: Basic debug message, espcially initialization
* `MSG` = 2: Input and output packets, read datastore
* `DETAIL` = 4: Details: message dump in hex, xpath parse trees, etc
* `EXTRA` = 8: Extra detailed logs
* Test: some errors in yang-lib where content-id was in wrong place
[Conversion of ethernet address (PhysAddress) and IP address (IPAddress) crashes agent](https://github.com/clicon/clixon/issues/340)
Hwaddress and IP adress for scalar and table set should now work
* Added new text syntax parsing and loading from CLI
* Unified text output functions to `xml2txt` and moved to clixon_text_syntax.[ch]
* The following are removed: `cli_xml2txt` and `xml2txt_cb`
* Text output format changed:
* Namespace/modulename added to top-level
* See [Support performant load_config_file(...) for TEXT format](https://github.com/clicon/clixon/issues/324)
* Added lastkey argument to yang_key_match()
* Fixed segv in process-sigchld
* Added ietf-yang-library to CLICON_CLI_AUTOCLI_EXCLUDE default value
* Added yang_spec_print() function
* Fixed: [Performance issue when parsing large JSON param](https://github.com/clicon/clixon/issues/266)
* Moved strlen() from for end condition
* Fixed debugging of xpath parser
- Added autoconf config options, temporary for nghttp2 development: `--disable-evhtp`and `--enable-nghttp2`.
- Added special case for api-path:s beginning with //
* Example: `GET restconf/data/x:a=`
* Previous meaning (wrong): Return all `a` elements.
* New meaning (correct): Return the `a` instance with empty key string: "".
* [RESTCONF GET request of single-key list with empty string returns all elements #213](https://github.com/clicon/clixon/issues/213)
* [RESTCONF GETof lists with empty string keys does not work #214](https://github.com/clicon/clixon/issues/214)
