[Issue #1033 #450] Disable backpropagation for general layers (#1181)
[Issue #1033 #450] Disable backpropagation for general layers (#1181)

* add propagateback and generate backward graph

new unit test pass

unit test except resnet pass

unit test pass

support rebuild

support multiple inputs

fix updateGradInput and acc

fix unit test

rename to trainable, add API to set trainable at graph

unit test except inception and resnet pass

unit test pass

code clean

fix conflicts

add unit test for setTrainable, setFreeze, unFreeze

use input buffer

add getSubmodule in AbstractModule

resolve conflicts

update isInputNode

update comment

update setTrainable

fix

fix mixture of graph and container

add setFreeze python API

update python and add doc

meet code review

* meet code review

* fix unit test

* meet code review

* fix code style

* fix inception unit test

* meet code review

* meet code review

* rm cloneNode

* resolve conflicts

* fix reset

* meet code review

* meet code review

* fix

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