* wip

* parse working with one test

* Add version information query and unit tests for parsing version strings

* add more comments

* doc strings

* style

Now both LLVM optimizer and codegen are aligned with
"NGRAPH_MLIR_OPT_LEVEL" macro.

* Update cpu backend to support i32 with topk

* Add topk i32 unit test

* Minor fix in unit-test

* disable test for plaidml

MLIR Commit:
commit c636f127ee412ef7279ec0d550f42740824cd9ea
Author: Alex Zinenko <zinenko@google.com>
Date:   Fri Aug 9 08:59:45 2019 -0700

    LLVM dialect and translation: support global strings

LLVM Commit:
commit c636f127ee412ef7279ec0d550f42740824cd9ea
Author: Alex Zinenko <zinenko@google.com>
Date:   Fri Aug 9 08:59:45 2019 -0700

    LLVM dialect and translation: support global strings

* Add negative op

* Add test case

* Address feedback

* Merge master

* Consolidate to one routine for unary ops

* Change from Negative to Neg

* [MLIR] Enable affine loop tiling

This PR enables loop tiling optimization in affine dialect. It
introduces the following flags for configuration.
  - affine-loop-tile: enables/disables the optimization. Disabled by
    default.
  - loop-tile-cache-level: provides the cache level to which apply loop
    tiling to. Cache level size is obtained from LLVM's TTI.
  - loop-tile-cache-size: provides a cache level size that overrides
    cache information from TTI.

The current use of TTI is a bit hacky since we have to pass a fake
LLVM's function to make it work. However, this should be enough to get
some basic target information until we have a target model in MLIR or
find a better approach.

* Address feedback

* Rename flags

* Fix sum reference to handle corner cases with +-inf

* Review comments, and try to make Windows happy

* Update GPU unit_test.manifest

* More template grindery, to make macOS happy

* wip

* compiles and links

* style

* wip

* parse working with one test

* Add version information query and unit tests for parsing version strings

* add more comments

* doc strings

* style

Remove not-directly-used includes

* Fix crash when NGRAPH_ENABLE_{VISUALIZE,SERIALIZE}_TRACING=1

* Initialization for kw

Cyphers/25tomaster

Update CODEOWNERS

Convert remaining experimental op dir to output args

Cyphers/s barannikov initialize dyn pad mode

Fix crash when NGRAPH_ENABLE_{VISUALIZE,SERIALIZE}_TRACING=1

Add missing initialization of pad mode in DynPad constructor

* adding group convolution implementation for plaidml

* update CMakeLists.txt to include new group convolution files

* adding new ngraph unit tests for grouped convolutions

* adding group conv unit test back in for plaidml backend

* specify group convolution support in plaidml

* add denise as codeowner for plaidml runtime dir

* remove commented-out lines of unit test manifest

* style changes

* resolve all discussions in PR

* skip data dilation unit test on cpu backend