* Have abs use layout.

* Use layout to get vector info

* Add format selector for mapped arrays
Convert some ops
Drop runtime.cpp since we don't expose the functions any more.

* Add vector concat

* concat matrix

* Switch more ops to simpler eigen wrapping

* Add reduce op class and type propagation

* Implement FunctionCall through VM

* Changes Function to require explicit return type at construction time

CMake: Update MKL-DNN tag and remove upstreamed patch

* cleanup pass registration code.

* Replace explicit code to do passes with pass_manager passes

* make external function work with const types internally, it should not change the graph

* Basic layouts, tuples

* Review comments.

* Add incude for size_t.

* Bop use-after-free in GetTupleElement

* Inline call to get_element_types()

* Implement vector and matrix concatenation through VM

* Address PR comments

* Comments on Concat semantics

* Remove some redundant template parameters in concat_matrix and concat_vector

* Formatting fixes in external_function.cpp

* Vector dot product implementation

* Implement matrix mult instruction in VM

* Add implementations for scalar-tensor and matrix/vector products.

* This is kind of a cheap hack for the moment, at least in the tensor
  constant case: each constant instruction carries around its value,
  and copies that to the result buffer everytime we need it. Ultimately
  we will probably want a pass that allocates space in the call frame
  for constants, similar to what we do for parameters.

* Add elementwise ops to runtime

* equals operator implementation at graph and runtime level

* "Select" operator (elementwise ?:) at graph and runtime level

* A few file renames (`notequal` -> `not_equal`, `lessthan` -> `less_than`)

* Macro wrapping boilerplate for op registration in `external_function.cpp`
  (this covers everything except `op::Parameter`).

* Forces CI to use clang-3.9

add tensor buffer size unit test

fix warnings when building mkldnn test

get tensor is_output set. Add Manager state and Function to pass manager

use pass manager internal state

fix eigen warnings during build

rename logging macros

Moves src tree under `ngraph` dir

* Done to achieve goal of having our #include directives all start
  with `"ngraph/`, like LLVM does.

individual install path for external projects

new directory layout

add liveness pass

Simplify expression construction for tests.

* Simplify external function use.

* By default, release original function.
Optional argument to delay release.

add naming of tensors and tensor views
add visualization pass
add graph dump pass