Created by: sidgoyal78

This PR basically modifies the current example.cc and inference.* files (in addition to changes in program_desc.*) to implement a basic Load() function which follows the current design doc by @Xreki (PR #7315). The example code is modified accordingly.

The example code runs successfully, but there is another TODO item.

TODO: The new getters and setters for feed and fetch vars in program_desc should have corresponding implementations in protobuf.cc.