support dataframe in pytorch fit, pytorch evaluate, add pytorch predict (#3360)
support dataframe in pytorch fit, pytorch evaluate, add pytorch predict (#3360)

* support dataframe in pytorch mxnet fit, pytorch evaluate

* add back

* fix style

* change back

* fix test and revert mxnet

* fix style

* fix test

* fix tests

* add prediction in pytorch ray estimator

* fix tests

* add doc

* fix doc

* clean up code

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