add config comments

configuration/pegasus_jaas.conf

@@ -1,10 +1,22 @@
 client {
+    // Krb5LoginModule authenticates users using Kerberos protocols.
 	com.sun.security.auth.module.Krb5LoginModule required
+
+	// config options in Krb5LoginModule:
+	// output debug message if debug is set to true
 	debug=true
+	// Set this to true, if you want the TGT to be obtained from the ticket cache.
+	// Set this option to false if you do not want this module to use the ticket cache. (Default is False).
 	useTicketCache=true
+	// Set this to true if you want the module to get the principal`s key from the the keytab. (Default value is False)
 	useKeyTab=true
+	// Set this to the file name of the keytab to get principal`s secret key.
 	keyTab=""
+	// Set this to true, if you want to renew the TGT.
+	// If this is set, useTicketCache must also be set to true. otherwise a configuration error will be returned.
 	renewTGT=true
+	// The name of the principal that should be used. The principal can be a simple username such as "testuser" or a service name such as "host/testhost.eng.sun.com".
 	principal=""
+	// Set this to true to if you want the keytab or the principal`s key to be stored in the Subject`s private credentials.
 	storeKey=true;
 };