load fountain details from server only if refreshing or server data corrupted

[ralfhauser]

see also water-fountains/datablue#41

[ralfhauser]

2. location and properties should not be loaded so often:
   a) first approach: copy 2 files Lazy load locations/properties #334
   b) todo: include them upon json packaging the proximap app instead of copying

3. the proximap/src/app/data.services.ts:incomplete() function should be shared between proxima and datablue (for flatten out / reduce calls to osm, wiki*, flickr, mapillary, ... datablue#45) by inclusion

[ralfhauser]

4. do not flush redux cache and alike (in proximap/src/app/route-validator.services.ts:validateWikidata() the this.dataService.fountainsAll) until it is properly determined that they really belong to the wrong city