* 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

Fixes for building with reference OS in docker image

remove class Op and merge functionality with Node

Changes to allow build (in docker run) to run as the user, not root, so BUILD directory is easily removable.

Function execution

CMake: Replace a previously missed instance of 'git am'

CMake: Use 'patch' instead of 'git am'

Git invocations without an available gitconfig (ex. a test environment)
will fail whereas patch should always work. This adds a build dependecy on patch.

fix namespace collision in runtime test

VM for interpreting ops

* Implemented binops/unops with different return type from args

* Implemented generic bases class for comparison and arith ops, changed current comparison ops to subclass it

* Added a TraitedType for booleans

* Moved arith and comparison ops to separate header files from `op.h`