* Move reshape utils down to reshape namespace.

* Reshape operation.

* Reshape operator binding.

* Error fixes.

* Reshape unit tests.

* Move flatten utility function to reshape namespace.

* Fix unused catched exception object

* Add Constant support for int64

* Review fix.

* clang-format

* Review fix part 2.

* Enable output shape as a second node input (only Constant).

* Unit test for "dynamic" output shape (from Constant node).

* Review fixes.

* Make sure second Reshape op input is Constant node.