Extract net and blobs assignment to separate functions
Extract net and blobs assignment to separate functions

Summary:
Use AddNet and AddBlobs to add net and blobs to meta_net_def.
This a codemod and does not change the functionality.
It is for preparation of the protobuf change.
Depends on: D4770648

Reviewed By: salexspb

Differential Revision: D4771110

fbshipit-source-id: 00cecb2105f2c332bd50c3c51b9a10e1004fa90f

Yangqing/caffe2,pietern/caffe2,xzturn/caffe2,xzturn/caffe2,davinwang/caffe2,xzturn/caffe2,sf-wind/caffe2,davinwang/caffe2,caffe2/caffe2,davinwang/caffe2,davinwang/caffe2,Yangqing/caffe2,sf-wind/caffe2,Yangqing/caffe2,bwasti/caffe2,davinwang/caffe2,sf-wind/caffe2,pietern/caffe2,bwasti/caffe2,pietern/caffe2,sf-wind/caffe2,Yangqing/caffe2,xzturn/caffe2,pietern/caffe2,pietern/caffe2,bwasti/caffe2,Yangqing/caffe2,xzturn/caffe2,bwasti/caffe2,bwasti/caffe2,sf-wind/caffe2