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**Description**
Add ONNXRuntime inference benchmark based on ORT python API.

**Major Revision**
- Add `ORTInferenceBenchmark` class to export pytorch model to onnx model and do inference
- Add tests and example for `ort-inference` benchmark
- Update the introduction docs.

**Description**
This commit does the following:
1) Adds CPU-initiated copy benchmark;
2) Adds dtod benchmark;
3) Support scanning NUMA nodes and GPUs inside the benchmark program;
4) Change the name of gpu-sm-copy to gpu-copy.

**Description**
This commit fixes the URL of ROCm GPG file.

**Description**
Add gpcnet as git submodule and building logic.

**Major Revision**
- add gpcnet as a submodule
- add build logic in third_party/Makefile

__Description__

Resolve "too many open files" issue when runnning NCCL/RCCL on multiple nodes using Docker images, increase nofile number in limits.conf.

**Description**
Install openmpi-4.0.0 for ROCm images.

**Description**
Setup docker environment in docker container.

**Major Revision**
- Install docker client for cuda and rocm images.
- Mount /var/run/docker.sock from host

**Description**
Add dockerfile `rocm4.0-pytorch1.7.0.dockerfile` and `rocm4.2-pytorch1.7.0.dockerfile` for `rocm` platform.