* Initial sub-graph extraction

* Works without detaching input edges from sub-graph

* Added removing input edges to graph

* Works with whole func sub-graphs. Inputs edges to sub-graph are still there

* Works on 2 exclusive sub-graphs. Still not on merged sub-graphs

* Revert removing inputs to sub-graph. nGraph validation crashes

* Added 3 sub-graph test. Remove compiled_kernel fusion pass. Comments

* Revert some changes

* Added cycle detection. Removed unit-tests to backend_mlir.in.cpp. Still not fully functional

* Construct CK nodes after finding outputs to preserve the graph.

* Fix topological sort. UTs pass.

* Minor fixes

* PR fixes

* Enable mlir tests only when building with MLIR on

* new debugger to trace real tensors in each kernel

* update after style-apply

* add unit test to debugger

* after style-apply

* templatize data + fixed issues from PR

* solve conflict

* change names of env flags + fixed typo + pass unit-test

* add different types to dump, change arch of debug class, add support to allow debug to be set programmatically (all requested changed fixed)

* add curly braces to single-line blocks

* fix shadow names + add int32 for dump + fix for names with coding standarts of ngraph

* fix names of member variables + delete some constructors

* try to find issue with CI, do not merge!

* fix one issue with CI

* fix style-apply

* Support MLIR lowering of Relu

* Use EDSC comparison

* style-apply

* Use .inc file for Conversion classes list

* Disable i32 Relu for plaidml

* Use libc++ for macOS core python wheel

* numpy version

* Add a few more toy dynamic examples

* Enable constant folding for Reverse; enable reverse_shape test

* Add constant folding for Product, and enable two more tests

* Update the conf file picked up by CI

* Remove extraneous conf.py

* Add known issues to release notes

* Word fix

* Fix bulleted list formatting

[MLIR] Add ArgMin/ArgMax lowering support

Fix crash on MacOS

Minor PlaidML fixes

Add Batch Norm Inference Relu fusion.

Update generic CPU backend to latest ngraph API

Update mkl-dnn to v0.20

Fix Onnx CI seg fault 

This reverts commit 6d123d6e.

Add comments.

Add more unit tests.