* The design is similar to bash history:
* The CLI loads/saves its complete history to a file on entry and exit, respectively
* The size (number of lines) of the file is the same as the history in memory
* Only the latest session dumping its history will survive (bash merges multiple session history).
* Tilde-expansion is supported
* Files not found or without appropriate access will not cause an exit but will be logged at debug level
* New config options: CLICON_CLI_HIST_FILE with default value `~/.clixon_cli_history`
* New config options: CLICON_CLI_HIST_SIZE with default value 300.
* clixon-config YAML file has new revision: 2019-03-05.
* New URN and changed top-level symbol to `clixon-config`
* Removed obsolete `_CLICON_XML_NS_STRICT` variable and `CLICON_XML_NS_STRICT` config option.
* Replaced all calls to (obsolete) `cli_output` with `fprintf`
* Added _experimental_ config option `CLICON_CLI_UTF8` default set to 0.
* CLIgen UTF8 does not work with scrolling and control editing
* Added -p <dir> command-line option to all programs: backend, cli, netconf, restconf.
* Moved and updated all standard ietf and iana yang files from example and yang/ to `yang/standard`.
* Renamed example yang from example.yang -> clixon-example.yang
