Feature: Provide logging when incorrectly configured

[jokajak]

Simple PEBKAC request, I used lat and lon instead of latitude and longitude and wondered why it wasn't working. It would be nice if an error message was logged when required configuration values are missing.

Nice work!

[jclarke0000]

This logging already exists. If you're using PM2, you'll see it when you run pm2 logs mm. Otherwise if you're running it from the command line, you see such errors there.

Specific code is in node_help.js, lines 37-41:

      if (payload.apikey == null || payload.apikey == "") {
        console.log( "[MMM-OpenWeatherForecast] " + moment().format("D-MMM-YY HH:mm") + " ** ERROR ** No API key configured. Get an API key at https://darksky.net" );
      } else if (payload.latitude == null || payload.latitude == "" || payload.longitude == null || payload.longitude == "") {
        console.log( "[MMM-OpenWeatherForecast] " + moment().format("D-MMM-YY HH:mm") + " ** ERROR ** Latitude and/or longitude not provided." );
      } else {