Added support for private url without username/password.

Added support for using google calender without password.

You might not allways want to write the password in clear text in a configuration file, depending on the security of your system. This gives you an oppertunity to use the calender function without password.
You have to use the private url from your google calendar or make the calendar public.

With this patch GCal now supports
1) url, username, password (as before)
2) url (without username/password)