* Formatting; fix erroneous "type_prop" classification for reduce and slice tests

* Clarify comment

* Add step parameter to slice, with type checking but not (yet) implementation in VM

* Add elementwise exp to VM

* Formatting

Bob/warnings

* Type checking for reshape op

* Formatting

* Implement reduce op for matrices and smaller in VM

* Formatting

* Missing include for Ubuntu

* Remove IndexBuiltin class

Docker: Add more deps

Add a minimal Backend API and make the interpreter use it.
read/write tensors (for frameworks)

* cleanup

* fix node includes

Moved all apt-get install commands into same RUN line as apt-get update.  There is a subtle timebomb if apt-get update is performed in a separate RUN line, due to how docker layers work. (#179)

* isolate graph building / execution scope in some unit tests (this triggered the user-after-free which was also observed from TF)

* Change descriptor::layout::TensorViewLayout to store a shared pointer to the TensorViewType rather than a reference to the TensorView

* port functions from funky passman branch

* update pass tests

* wip

* fixed

* remove obsolete test

* remove debug prints

Include cmath for 'expf' etc.

* Type propagation for convert

* Implement "convert" through VM

* Temporary commit to unconfuse git merge

* Undo temporary commit to unconfuse git merge

* Add support for some polymorphic operators (arithmetic, etc.)

* Extend to all other ops except Tuple, which is tricky (not quite sure where to get the needed type info)

* Some tidying(???) up

* Extend to handle Tuple op

* Slightly more descriptive macro name

Detect macOS and adapt sed usage in clang-format version check script; also fix small typo in err msg (#169)

Emacs likes to add hidden symlinks with names like '.#myfile.cpp' that don't actually point to real files as a locking mechanism, which cause the format check/apply scripts to fail. This tweaks the format scripts to ignore files that are symlinks (adds a -type f predicate to the find commands), which gets around this issue.

apply new .clang-format

* Implement broadcasting of scalars through VM

* Implement vector-to-matrix broadcasting through VM

* Add missing files

* Address review comments

Remove old {get,set}_{array_matrix}{_2d,} methods; update dot product to use new Eigen wrapper (#158)

Use weak_ptr for node in inputs/outputs, turn off alignment style.