Add readonly api to gateway

Based on https://github.com/ipfs/go-ipfs/pull/1389

License: MIT
Signed-off-by: rht <rhtbot@gmail.com>

cmd/ipfs/daemon.go

@@ -401,6 +401,7 @@ func serveHTTPGateway(req cmds.Request) (error, <-chan error) {
 	}
 
 	var opts = []corehttp.ServeOption{
+		corehttp.CommandsROOption(*req.InvocContext()),
 		corehttp.VersionOption(),
 		corehttp.IPNSHostnameOption(),
 		corehttp.GatewayOption(writable),