Create function to calculate meter based on lat/lng

[gerbsen]

• place in r360.Util
• use it in examples for geojson buffering

[gerbsen]

please also integrate this here directly: https://developers.route360.net/services/geojson

[abenrob]

https://github.com/route360/r360-js/blob/master/src/util/Util.js#L371-L395

And updated in demos as well (to be published soon.)