[#7] Add local tool for building database file

Added frostfs-locode-db CLI utility that can generate and view UN/LOCODE
database files. Go package
git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/locode copied to
this repository to eliminate interdependency between frostfs-node and
frostfs-locode-db projects. The process of building database files
reduced to starting make command.

Signed-off-by: George Bartolomey <george@bh4.ru>

pkg/locode/db/continents/geojson/opts.go

@@ -0,0 +1,10 @@
+package continentsdb
+
+// Option sets an optional parameter of DB.
+type Option func(*options)
+
+type options struct{}
+
+func defaultOpts() *options {
+	return &options{}
+}