Draft: Fix #345: add an option to allow dumping information about all hived options in JSON format

This change adds an option --dump-options in appbase library. It allows to dump information about all available command-line and config options. Example output:

$ ./hived --dump-options
{
  "config_file": [{
      "name": "log-appender",
      "description": "Appender definition json: {\"appender\", \"stream\", \"file\"} Can only specify a file OR a stream",
      "required": false,
      "value": {
        "multiple_allowed": false,
        "composed": true,
        "value_type": "string_array",
        "default_value": [
          "{\"appender\":\"stderr\",\"stream\":\"std_error\",\"time_format\":\"iso_8601_microseconds\"}",
          "{\"appender\":\"p2p\",\"file\":\"logs/p2p/p2p.log\",\"time_format\":\"iso_8601_milliseconds\", \"delta_times\": false}"
        ]
      }
    },
[...]
  ],
  "command_line": [
[...]
    {
      "name": "help",
      "description": "Print this help message and exit.",
      "required": false,
      "value": null
    },
[...]
  ]
}

Requires test-tools!97