Revert "Revert "adding CountriesColumnMerger""

This reverts commit a80caa2361.

src/CountriesColumnMerger.py

@@ -0,0 +1,10 @@
+from CountriesMerger import CountriesMerger
+
+class CountriesColumnMerger:
+
+    @staticmethod
+    def mergeCountriesColumnOfSrcIntoCountriesColumnOfDst(src, dst):
+        COUNTRIES = 'Countries'
+        dst[COUNTRIES] = CountriesMerger.mergeSrcIntoDst(
+            dst = dst[COUNTRIES],
+            src = src[COUNTRIES])