[#316] locode: Implement NeoFS location database based on BoltDB instance

Define NeoFS location database based on BoltDB. Implement methods to save
the record by key (Put) and to read the record by key (Get).

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

pkg/util/locode/db/boltdb/opts.go

@@ -0,0 +1,22 @@
+package locodebolt
+
+import (
+	"os"
+
+	"go.etcd.io/bbolt"
+)
+
+// Option sets an optional parameter of DB.
+type Option func(*options)
+
+type options struct {
+	mode os.FileMode
+
+	boltOpts *bbolt.Options
+}
+
+func defaultOpts() *options {
+	return &options{
+		mode: os.ModePerm, // 0777
+	}
+}