Harvester fails to parse ArcGIS Server layer extent

[mhogeweg]

Harvester currently assumes the extent is a 2D list, while this 11.5 server returns it as a 1D list:
https://services7.arcgis.com/n1YM8pTrFmm7L4hs/arcgis/rest/services?f=json

Issue is in ItemInfo.java.

[mhogeweg]

see PR #255