Support seq(tensor), implement 2 sequence ops that use the new type. (#1983)
* Mention OrtCreateSessionFromArray in C API doc
* fix seq of tensors
* changes on 9/30
* All tests passing
* Add SequenceAt op
* Fix shared_lib non_tensor_types test
* Address some PR comments
* Address PR comments
* Add support in python bindings to accept seq(tensor)
* Change data type from vector<Tensor> to TensorSeq
* Change data type from vector<Tensor> to TensorSeq
* Added some documentation
* Added missing test model
* Fix Linux build
* Fix Mac build
* Fix Mac build