* Previous implementation did not handle nested if-feature expressions
* As part of fixing: [YANG if-feature does not support nested boolean expression](https://github.com/clicon/clixon/issues/341)
* Added new yacc/lex parser for if-feature-expr string
* Instead of using prefixes for augmented XML, assign the default namespace
Test: moved datastore format tests from test_cli to new test_datastore_format
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
* 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)
