Add "inferred username" to session code

[jacalata]

Existing behavior:

if( ( m_sessionData.getUsername() == null ) && !m_sessionData.getUseCertificate() ){   | String username = System.getProperty("user.name");   | m_sessionData.setUsername(username);   | m_logger.info(m_i18n.getString("session.inferred_username", username));