* Use NGRAPH export macros instead of CPU

* Move code to ngmlir namespace

* Move MLIR to src/contrib/mlir

* Create MLIR as cmake external project. Clone and build via ngraph cmake

* Moved code and enabled compilation. Need to clone and build MLIR/LLVM during cmake step, so find_package can work

* clone and build llvm/mlir during configuration. Compiles now. Needs more testing

* Force DEX only if MLIR is ON

* Remove extra cmake file. Style-apply

* Remove redundant files in cpu/mlir

* Update CODEOWNERS. Check for ninja and fail if not found

* Fixing post merge issues

* Implements a simple memory manager that just does malloc for now. Pointers are freed during cleanup.
* Enable JIT call-back to memory manager to allocate temps.
* Memory manager pointer is passed to the JIT'ed code upon invocation. That makes the code re-entrant from different threads in case the code is shared among identical sub-graphs that are executed in parallel.

* constexpr ctor for EnumMask

* added pass properties to core passes.

* added unit tests.

* minor fixes.

* update licenses for 2019

* style

* use line comments instead of multiline comments for license header

* update more

* update new files

* more header updates

* style

*  zero dimension tensor elimination init

* more ops + refactor + tests

* revert pattern.cpp

* add internal zero-length test

* address Scott's feedback

* fix comp errors

* proper static init

* get rid of unique-ptr

* refactor hashmap into virtual get_default_values on op classes

* fix formatting

* removing extra copies due to op::Result

* remove comment

* fix comment

* switch to a flag version

* add copyright header #pragma once

* add impl file, rename result_elimination.hpp to result_copy_elimination.hpp to match the opt name

* add cpp suffix to result_copy_elimination

* use member in-class member init

* cleanup

* fix node includes

* port functions from funky passman branch

* update pass tests

* wip

* fixed

* remove obsolete test

* remove debug prints

* Done to achieve goal of having our #include directives all start
  with `"ngraph/`, like LLVM does.

add naming of tensors and tensor views
add visualization pass
add graph dump pass

Add memory layout and liveness passes.

add test framework

stuff wired up

benchmark segfault for 5M nodes. fun

make traverse_nodes not recursive

print timings on benchmark

unit test for pass manager

All tuples are expanded out to their component tensors.

Output: Describes one tensor output of an node
Input: Described one tensor input to a node, including the output supplying the value.