added methods for restricting drop behavior
added methods for restricting drop behavior

LivelyKernel/LivelyKernel,pascience/LivelyKernel,NikolaySuslov/LivelyKernel,LivelyKernel/LivelyKernel,pascience/LivelyKernel,pascience/LivelyKernel,LivelyKernel/LivelyKernel,NikolaySuslov/LivelyKernel,NikolaySuslov/LivelyKernel