cli: implement AddressFlag

This makes code less verbose and performs all parsing
before invoking main function.

cli/flags/util.go

@@ -0,0 +1,11 @@
+package flags
+
+import "strings"
+
+func eachName(longName string, fn func(string)) {
+	parts := strings.Split(longName, ",")
+	for _, name := range parts {
+		name = strings.Trim(name, " ")
+		fn(name)
+	}
+}