add weightdecay to Adam (#2415)
add weightdecay to Adam (#2415)

* add weightdecay

* revert

* some change

* some update

* some update
yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL