Refactor the serde logic of JTensor and Sample (#1510)
Refactor the serde logic of JTensor and Sample (#1510)

* update

* fix

* add bigdltype

* update comment

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