config+lnd: update tor config to include onion services flags

In this commit, we update the set of Tor flags to use sane defaults when
not specified. We also include some new flags related to the recent
onion services changes. This allows users to easily get set up on Tor by
only specifying the tor.active flag. If needed, the defaults can still
be overridden.

lnd.go

@@ -304,11 +304,10 @@ func lndMain() error {
 	}
 	idPrivKey.Curve = btcec.S256()
 
-	if cfg.Tor.Socks != "" && cfg.Tor.DNS != "" {
+	if cfg.Tor.Active {
 		srvrLog.Infof("Proxying all network traffic via Tor "+
-			"(stream_isolation=%v)! NOTE: If running with a full-node "+
-			"backend, ensure that is proxying over Tor as well",
-			cfg.Tor.StreamIsolation)
+			"(stream_isolation=%v)! NOTE: Ensure the backend node "+
+			"is proxying over Tor as well", cfg.Tor.StreamIsolation)
 	}
 
 	// Set up the core server which will listen for incoming peer