fs: make --links flag global and add new --local-links and --vfs-links flag

Before this change the --links flag when using the VFS override the
--links flag for the local backend which meant the local backend
needed explicit config to use links.

This fixes the problem by making the --links flag global and adding a
new --local-links flag and --vfs-links flags to control the features
individually if required.

fs/config.go

@@ -105,6 +105,12 @@ var ConfigOptionsInfo = Options{{
 	Default:  false,
 	Help:     "Enable interactive mode",
 	Groups:   "Config,Important",
+}, {
+	Name:     "links",
+	Help:     "Translate symlinks to/from regular files with a '" + LinkSuffix + "' extension.",
+	Default:  false,
+	ShortOpt: "l",
+	Groups:   "Copy",
 }, {
 	Name:    "contimeout",
 	Default: 60 * time.Second,
@@ -537,6 +543,7 @@ type ConfigInfo struct {
 	UseJSONLog                 bool              `config:"use_json_log"`
 	DryRun                     bool              `config:"dry_run"`
 	Interactive                bool              `config:"interactive"`
+	Links                      bool              `config:"links"`
 	CheckSum                   bool              `config:"checksum"`
 	SizeOnly                   bool              `config:"size_only"`
 	IgnoreTimes                bool              `config:"ignore_times"`