Rely on example csv first

csv/example.csv

@@ -0,0 +1,5 @@
+id,source,layer,name,housenumber,street,postcode,lat,lon,addendum_json_pelias
+1,pelias,example_layer,Example Location,,,,5,5
+2,pelias,address,123 Main St,123,Main St,90210,6,7
+3,pelias,invalid,123 Main St,,,,,
+4,pelias,with_custom_data,501 Broadway,,,,10,11,"{ ""your_custom_data"":""goes here"", ""year"": 2019, ""nested"": { ""supported"": true } }"