Merging approx_hpvm and this branch

llvm/projects/hpvm-tensor-rt/docs/Changes.md

llvm/projects/hpvm-tensor-rt/lib/tensor_runtime.ll

...pvm-tensor-rt/tensor_runtime/include/tensor_signatures.cc

llvm/projects/keras/cmake_template/CMakeLists.txt

llvm/projects/keras/frontend/approxhpvm_translator.py

llvm/projects/keras/frontend/hpvm_dfg_translator.py

llvm/projects/keras/frontend/promise_translator.py

llvm/projects/keras/frontend/utils.py

llvm/projects/keras/frontend/weight_utils.py

llvm/projects/keras/keras_environment.yml

llvm/projects/keras/keras_environment_minimal.yml

llvm/projects/keras/legacy/generated/vgg16/approxhpvm_src.cc

llvm/projects/keras/legacy/generated/vgg16/src.cc

llvm/projects/keras/legacy/keras_environment.yml

llvm/projects/keras/legacy/keras_environment_deps.yml

llvm/projects/keras/src/Benchmark.py

llvm/projects/keras/src/alexnet.py

llvm/projects/keras/src/alexnet_imagenet.py

llvm/projects/keras/src/legacy/lenet_conv_test.py

llvm/projects/keras/src/legacy/mobilenet_imagenet.py