* fix save interfaces of flatbuffers, test=develop

* fix the header file, test=develop

* add build macros for flatbuffers, test=develop

* update compatible_pb.cc, test=develop

* using unique_ptr in fbs::desc, test=develop

* add fbs to compatible_pb, test=develop

* update model_parser functions, test=develop

* fix bugs, test=develop

* [test] flatbuffers io, test=develop

* determine the basic interfaces and help functions of flatbuffers, test=develop