add dot and l2_normalize operators (#441)
add dot and l2_normalize operators (#441)

* update

* add

* update

* fix predict

* add dot and normalize

* fix predict

* add doc

* add doc

* update

* update

* update md

* style

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