add script to run old graph builder, update usage message and comments

build-old

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+# run the older Spring-assembled graph builder
+java -Xmx4G -classpath otp-core/target/otp.jar org.opentripplanner.graph_builder.GraphBuilderMain $1

otp

@@ -1,2 +1,6 @@
 #!/bin/bash
+
+# Run OTP in standalone mode with the supplied arguments.
+# Standalone OTP can build a graph, visualize a graph, run an OTP API server,
+# or any combination of these.
 java -Xmx6G -jar otp-core/target/otp.jar "$@"

otp-core/src/main/java/org/opentripplanner/graph_builder/GraphBuilderMain.java

@@ -39,7 +39,7 @@ public class GraphBuilderMain {
     public static void main(String[] args) throws IOException {
 
         if (args.length == 0) {
-            System.err.println("usage: config.xml");
+            System.err.println("usage:\njava [-Xmx<heapsize>] -classpath otp-core/target/otp.jar org.opentripplanner.graph_builder.GraphBuilderMain <config.xml>");
             System.exit(-1);
         }