go-ipfs-config: Make gateway read-only by default and add option to make it writable

config/gateway.go

@@ -3,4 +3,5 @@ package config
 // Gateway contains options for the HTTP gateway server.
 type Gateway struct {
 	RootRedirect string
+	Writable bool
 }

config/init.go

@@ -54,6 +54,7 @@ func Init(out io.Writer, nBitsForKeypair int) (*Config, error) {
 
 		Gateway: Gateway{
 			RootRedirect: "",
+			Writable: false,
 		},
 	}