* Adapt Tensor class to have partial shapes

* Add PartialShapes to Input, Output, Function, Node classes

* Terminological cleanup

* Add PartialShape propagation for Parameter and Result

* Implement partial-shape propagation for elementwise ops

* More comments

* One more comment tweak

* Add tests for the merge functions

* Add merging of undetermined element types

* Fix a goophup in deserializer implementation

* Implement fallback for ops that do not support partial shape/type validation

* Updates for some older unit tests, now that operator[] exists

* Add missing validate_punt_if_incomplete to AllReduce

* Implement partial shape/type propagation for AllReduce

* Implement partial shape/type propagation for Reshape

* Remove unneeded validate_punt from Result

* Implement partial shape/type propagation for Reverse

* Implement partial shape/type validation for ReverseSequence

* Implement partial shape/type validation for ArithmeticReduction

* Better docstrings for the stuff introduced in #1692; remove prototype for unimplemented, unused PartialShape::append()

* One more docstring thing I forgot to save

* Switch terminology from 'determined/undetermined' to 'static/dynamic'

* Switch terminology from 'complete/incomplete' to 'static/dynamic' for shapes; fix up some mushily worded comments

* Fix overzealous edits from the last commit

* Rename one test that escaped the Great Renaming

* Remove unnecessary validate_punt_if_dynamic from Reshape

* Fix comment typo

* Rewrite operator+ and operator* for Dimension as members, not friends

* Formatting tweak

* Show argument types/shapes in long NodeDescription; tank unit tests to block merge

* Fix dynamic element type propagation for elementwise ops, add some unit tests for same

* Fix error message

* Roll 'Not' back to existing behavior (non-boolean input types allowed)

* Add a TODO tag to a todo item

* Add unit tests for partial shape/type propagation with ReverseSequence

* Add unit tests for partial-shape/type propagation for ArithmeticReduction (via Sum)

* Implement partial shape/type validation for Dot

* Implement unit tests for partial-shape/type propagation for Dot

* Implement partial type/shape propagation for GetOutputElement

* Function signatures

* Add implementations, unit tests for relaxes/refines functions

* Generalize project/reduce/inject functions to cover PartialShape, move to shape_util.[ch]pp

* Deal with std::find_if #include issues

* Fix more include madness

* Some light reformatting

* Review comments