Add AuthTool command-line tool to create shared secret for challenge/response authentication

src/main/java/org/sdnplatform/sync/client/AuthTool.java

+package org.sdnplatform.sync.client;
+
+import java.io.Console;
+
+import org.kohsuke.args4j.CmdLineException;
+import org.kohsuke.args4j.CmdLineParser;
+import org.kohsuke.args4j.Option;
+import org.sdnplatform.sync.internal.config.AuthScheme;
+import org.sdnplatform.sync.internal.util.CryptoUtil;
+
+/**
+ * Command-line tool for setting up authentication credentials
+ * @author readams
+ */
+public class AuthTool {
+    protected static class AuthToolSettings {
+        @Option(name="--help", 
+                usage="Show help")
+        protected boolean help;
+        
+        @Option(name="--keyStorePath", 
+                usage="Path to JCEKS key store where credentials should " + 
+                       "be stored",
+                required=true)
+        protected String keyStorePath;
+        
+        @Option(name="--keyStorePassword",
+                usage="Password for key store")
+        protected String keyStorePassword;    
+
+        @Option(name="--authScheme",
+                usage="Auth scheme for which we should set up credentials",
+                required=true)
+        protected AuthScheme authScheme;
+    }
+    
+    public static void main(String[] args) throws Exception {
+        AuthToolSettings settings = new AuthToolSettings();
+        CmdLineParser parser = new CmdLineParser(settings);
+        try {
+            parser.parseArgument(args);
+        } catch (CmdLineException e) {
+            System.err.println(e.getMessage());
+            parser.printUsage(System.err);
+            System.exit(1);
+        }
+        if (settings.help) {
+            parser.printUsage(System.err);
+            System.exit(1);
+        }
+        if (settings.keyStorePassword == null) {
+            Console con = System.console();
+            char[] password = con.readPassword("Enter key store password: ");
+            settings.keyStorePassword = new String(password);
+        }
+        
+        switch (settings.authScheme) {
+            case NO_AUTH:
+                System.err.println("No credentials required for NO_AUTH");
+                break;
+            case CHALLENGE_RESPONSE:
+                CryptoUtil.writeSharedSecret(settings.keyStorePath, 
+                                             settings.keyStorePassword, 
+                                             CryptoUtil.secureRandom(16));
+                System.out.println("Wrote random 128-bit secret to " +
+                                   settings.keyStorePath);
+                break;
+        }        
+    }
+}

src/main/java/org/sdnplatform/sync/client/SyncClient.java

@@ -436,7 +436,7 @@ public class SyncClient {
     
     protected static class SyncClientSettings {
         @Option(name="--help", 
-                usage="Server hostname")
+                usage="Show help")
         protected boolean help;
         
         @Option(name="--hostname", aliases="-h",