Add multiple rnn cell and support get/setHiddenState in Recurrent(#1591)
Add multiple rnn cell and support get/setHiddenState in Recurrent(#1591)

* add multicell
* add get/setHiddenStates
yangw1234/BigDL,intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL