[#316] locode: Define UN/LOCODE table data types

Define the data types needed to work with LOCODE's in NeoFS (country code,
location code, coordinates). Implement string parsers for new types.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/util/locode/column/util.go

@@ -0,0 +1,9 @@
+package locodecolumn
+
+func isDigit(sym uint8) bool {
+	return sym >= '0' && sym <= '9'
+}
+
+func isUpperAlpha(sym uint8) bool {
+	return sym >= 'A' && sym <= 'Z'
+}