Enable math operation for model construction (#208)
Enable math operation for model construction (#208)

* select

* refactor scala api

* add from

* unittest

* style

* fix timedistributed

* refactor

* style

* fix scripts

* fix scripts

* fix test

* del

* fix ser

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