* Re-organize files. Create MLIR backend classes

* WIP

* Refactored. Code compiles

* Moved context to Runtime class to outlive compilation and execution

* style-apply

* Base Runtime class. Few other modifications

* Minor fixes

* Fixed Runtime::run() to take type-erased pointer

* renamed core compiler

* rename backend compiler

* rename runtime compiler

* PR feedback

* Fix build fails

* Op decl. No verification

* WIP

* WIP: Add lowerer support

* Code-gen works.

* Added padding support. Needs MLIR fix to work

* Remove Padding support for now

* Fix arrayref init. Disable tests where reshape optimization don't apply

* clean up and style apply

* Address PR feedback

We'll add contrib/mlir/tools directory in subsequent PRs for ngrpah-opt
and other tools.

* Add negative op

* Add test case

* Address feedback

* Merge master

* Consolidate to one routine for unary ops

* Change from Negative to Neg

* WIP

* All but two unit tests passing

* Explanatory comment

* Cleanup

* A bit of cleanup stemming from review comments

* Rewrite to use LoopNestBuilder

* Remove unnecessary check from CompiledKernel

* Removed some dead-ish code I missed

* Switch to camelCase in lowerer.cpp

* Fix assignment of resIndexHandles that was triggering an assert

* Add in some safety checks

* dyn_cast -> cast

* - templatize computing binary elementwise
- added lowering support for Add, Sub, Multiply, Divide

* - Added Support for Greater and less Op

* -Add support for Minimum and Maximum

* use edsc::intrinsics::select instead of terenary operator

* Addressed PR comments

* - return after the conditional check

* Support MLIR lowering of Relu

* Use EDSC comparison

* style-apply

* Use .inc file for Conversion classes list

* Disable i32 Relu for plaidml

MLIR Compile only supported ops