* TensorIterator

* ssize_t is not on windows

* RNN building test

* simplify

* Simplify output

* typo

* typos

* remove arg

* Sequence version

* style

* Serialization for all but TensorIterator

* Add ops for igpu

* style

* typo, ngpu

* missing headers, output vector

* Fix const json issues

* TensorIterator serialization

* Serialization for TensorIterator
Switch Outout<T> to use shared_ptr do nodes don't vanish
Switch Result to new node style
Add serialization/deserialization to test

* Switch Output to use a shared_ptr to prevent nodes from disappearing early.

* Eliminate wrapped enum
Switch allreduce to new op form

* Convert to new op form

* Disambiguate concat

* Add autobroadcast for SequencePush
Add validation for SequencePush

* compute shapes for SequenceRepeat

* Add explicit conversion from PartialShape to dimension vector
validate and infer types for SliceInput

* validate and infer types for SequenceOutput

* Add sequence attributes

* Move test to serializer so it doesn't fail when there is no serializer?

* const arg

* Beginning of TensorIterator validation

* Validation up to parameters

* Fix shape in test

* Remove mis-typed AxisSet

* Simplify, add doc

* Review comments

* Tweaks

* free/bound

* Try fused op

* Discussion

* more

* comments

* Start of LSTMCell test

* Add LSTMCell example

* Reorg

* Reorg

* Fused ops don't need handlers

* Serialization

* Use `as_type` and `is_type` for up-conversions of descriptions
Allocate output space for each output

* Clean up type checking

* Fix ser/deser issues

* Refactor, cleanup type info to make it safer to use for non-ops

* Implement validate_and_infer_types and modify unit tests.

* For ops in the loop body: revalidate and infer types.

Nested loop is not supported.

* Put body ops in a set and call revalidate and infer types on the set.

* Set slice[axis] to part_size.

Call set_partial_shape to set shape for body parameters.

Add more unit tests.

* Give tensor iterator body a lambda

* Update validate_and_infer_types and unit tests.

* Serialization of body

* Change static function to TensorIterator function.

* review comments