Geonames enrichment removes country if no match is found

[SvenLieber]

While working on #251 I noticed that the geonames enrichment script removes a country if no match is found. See example below:

• The file on the left is the original file created with a SPARQL query: an organization identifier and address parts, namely place name and country (whereas the country name is already uniform English as we work with URIs and multilingual labels)
• The file in the middle is the enriched version, where place and country names were made uniform by using the English spelling (lookup in Geoname dumps for some European countries)
• The file on the right is the final file in which based on the uniform names, geonames identifiers and coordinates are added to additional columns

Countries are removed in the file on the right, thus when that file is used to create RDF representations, the country is missing. If it is just used to add geonames identifiers and coordinates to already existing RDF (thus if the file on the left is the result of a SPARQL query), nothing will be broken, because the country URIs and labels are already part of the RDF.

[SvenLieber]

The parameter --column-country specifies the name of the column in the output file in which found country information is stored. However, if I provide the name of an existing country column that already contains values, it will be overwritten.

So technically I should provide a new column name such as found-country. But this is apparently not intuitive. In case the specified country column already exists, I should take the value it already has.