Add HiveMQ export command for client details

[gitseti]

Motivation

• The HiveMQ broker will be offering a rest api endpoint with its upcoming 4.4 release
• This PR adds an export command to fetch all client details from a HiveMQ deployment

Changes

• Add a new command line mqtt hivemq (entry point for HiveMQ specific commands)
• Add a new command line to the hivemq command line mqtt hivemq export (entry point for HiveMQ api export commands)
• Add a new subcommand to the export command mqtt hivemq export clients:

Export HiveMQ client details
 -url=<url>           The url of the HiveMQ API endpoint (default http://localhost:8888)
  -f, --file=<file>        The file to write the output to (defaults to a timestamped file in the current working directory)
  -r, --rate=<rateLimit>   The rate limit of the rest calls to the HiveMQ API endpoint in requests per second (default 1500 rps)
      --format=<format>    The export output format (default csv)
      --csvLineSeparator=<csvLineSeparator>
                           An own defined line separator for the csv writing (default ,)
      --csvQuoteChar=<csvQuoteCharacter>
                           An own defined quote character for the csv writing (default ")
      --csvEscChar=<csvEscapeChar>
                           An own defined escape character for the csv writing (default ")
      --csvLineEndChar=<csvLineEndCharacter>
                           An own defined line end character for the csv writing (default \n)

[gitseti]

Fix logging statements

[sauroter]

One small change.