PlaceDataSource WFS: added some @ since WFS output is not consistent as to fields, e.g. fields may be olmitted from individual records, so we must handle them as empty strings. likewise, a unique ID is not a given and for these use cases seems to be more normal than having unique IDs; workaround is to assign an ID so we can get data loaded, and accept that these IDs will basically be trashed on every reload
PlaceDataSource WFS: improved the automatic assignment of remoteid, to avoid number collisions; uses a SHA1 hash now