support nhwc format in SpatialConvolution (#1434)
support nhwc format in SpatialConvolution (#1434)

* support nhwc format in SpatialConvolution

* add python api and doc

* meet code review

* fix bug and add tests

* meet code review

* fix bug

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