Implement recover_input_schema_by_prefix
Implement recover_input_schema_by_prefix

Summary:
It's very useful for simple cases like benchmarking nets where we want to encode input/output record in the net and don't want to go through the hurdles of storing input/output record in MetaNetDef.

For those cases I propose remapping the input/output record before saving to 'input_record/{field_name}'. Then we can recover input/output record back just based on the names of the blobs.

Differential Revision: D5170473

fbshipit-source-id: ac5daa60051605ed93022aec1377a49f08f15663

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