Add end-to-end tutorial for EgoBipartiteGraphSAGE model.

[Seventeen17]

1. Trained with GraphLearn-Training: implement model with u2i2i and i2i2i meta-path;
2. Infered user embedding with Dynamic-Graph-Service:
   • Add getQuery http request;
   • Refine EgoGraph/EgoTensor for parsing sampled fbs records;
   • Refine App and add uts.