shell: add shell.toml support

fix https://github.com/chrislusf/seaweedfs/issues/1664

weed/command/scaffold.go

@@ -44,6 +44,8 @@ func runScaffold(cmd *Command, args []string) bool {
 		content = SECURITY_TOML_EXAMPLE
 	case "master":
 		content = MASTER_TOML_EXAMPLE
+	case "shell":
+		content = SHELL_TOML_EXAMPLE
 	}
 	if content == "" {
 		println("need a valid -config option")
@@ -459,5 +461,19 @@ copy_other = 1            # create n x 1 = n actual volumes
 # if you are doing your own replication or periodic sync of volumes.
 treat_replication_as_minimums = false
 
+`
+	SHELL_TOML_EXAMPLE = `
+
+[cluster]
+default = "c1"
+
+[cluster.c1]
+master = "localhost:9333"    # comma-separated master servers
+filer = "localhost:8888"     # filer host and port
+
+[cluster.c2]
+master = ""
+filer = ""
+
 `
 )