Geodata file map drag/drop

[chrismayer]

This adds support for geodata file drag/drop to the map as described in #99. Supported formats are GeoJSON, KML, GPX, IGC and TopoJSON. By adding the following config option the functionality can be enabled for your Wegue app:

  // ...
  "mapGeodataDragDop": {
    "formats": ["GeoJSON", "KML"],
    "zoomToData": false,
    "replaceData": true,
    "displayInLayerList": true,
    "layerName": "Uploaded Data"
  },
  // ...

Please review @justb4 and @JakobMiksch (and of course anybody else who is willing to review).

[JakobMiksch]

@chrismayer I tested it and it works like expected. Code looks fine as well. It is ready to merge from my side.

[chrismayer]

Thanks for the review @JakobMiksch. I'll address the suggestions of @justb4 posted in #99 (comment):

• sometimes it is an option to replace the data i.s.o. adding to the Layer, but you would need user-interaction or a config option
• is it an idea to show the added Layer in the LayerList? As config option (displayInLayerList, now hardcoded false). One could also configure the Layer name.

And then it should be good to go.

[justb4]

Ok, tested, fine to merge.

[JakobMiksch]

I tested it again, and it works well. Ready to merge.

[chrismayer]

Thank you for the reviews! I'll merge now.