CNN encoder : add option dependency for bridge type
CNN encoder : add option dependency for bridge type

jsenellart/OpenNMT,da03/OpenNMT,da03/OpenNMT,OpenNMT/OpenNMT,jsenellart-systran/OpenNMT,jungikim/OpenNMT,jsenellart/OpenNMT,jungikim/OpenNMT,da03/OpenNMT,jsenellart-systran/OpenNMT,jungikim/OpenNMT,OpenNMT/OpenNMT,jsenellart/OpenNMT,jsenellart-systran/OpenNMT,OpenNMT/OpenNMT