code: public void init (Properties config, ConnectionProvider conprov)
          throws PersistenceException
      {
          init(config, conprov, null);
      }
docs: Prepares this user manager for operation. Presently the user manager requires the
  following configuration information:
  
  <ul>
  <li><code>login_url</code>: Should be set to the URL to which to redirect a requester if
  they are required to login before accessing the requested page. For example:
  
  <pre>
  login_url = /usermgmt/login.ajsp?return=%R
  </pre>
  
  The <code>%R</code> will be replaced with the URL encoded URL the user is currently
  requesting (complete with query parameters) so that the login code can redirect the user
  back to this request once they are authenticated.
  </ul>
  
  @param config the user manager configuration properties.
  @param conprov the database connection provider that will be used to obtain a connection to
  the user database.