add Maximum, Minimum, MaxPooling1D keras2 layers (#389)
add Maximum, Minimum, MaxPooling1D keras2 layers (#389)

* add keras2 Conv1D layer and test

* style

* update

* update

* update

* update

* update

* add python Conv1D

* update

* add Maximum, Minimum, MaxPooling1D

* add Maximum, Minimum, MaxPooling1D

* add

* add maximum and minimum methods

* update

* update

* style

yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL,yangw1234/BigDL