* update licenses for 2019

* style

* Optionally get rid of codegen from the CPU backend

* Rename option variable

* Merge fixes

* Merge

* Remove extra changes

* remove dex only exclusions (#1429)

* Unconditionally pick  m_direct_execution if NGRAPH_DEX_ONLY

* Style fix

* Update cmake files to more modern approach

* disable building libraries that are not required

* handle more build cases

* add versions to backend libs. add start of package target.

* add create_backend to backends

* temporary workaround to tbb not linking correctly with gcc

* install codegen lib

* force tbb to link to the cpu backend so that it is available for codegen

* fix clang build error

* fix warning for codegen build

* update cuda header paths

* change error message for opening backend shared library

* set lib path

cleanup some enable flags in cmake. add flags to optionally disable building unit tests and tool (#917)

* add resource file generator and store all headers used by codegen in memory.

* add json lib 2.1.1

* turn off clang-format for json lib

* add unit test file

* add code to poison the use of ngraph.hpp from within the ngraph library

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

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

* 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`

Start of external function calling support

Add memory layout and liveness passes.

add test framework

stuff wired up

benchmark segfault for 5M nodes. fun

make traverse_nodes not recursive

print timings on benchmark

unit test for pass manager

All tuples are expanded out to their component tensors.

Output: Describes one tensor output of an node
Input: Described one tensor input to a node, including the output supplying the value.

add cmake finder for graphviz dot program and then conditionally compile visualization based on finding

* Cleaned up the CMakeLists.txt to properly do the include paths and fixed the install targets.
Also cleaned up the header files located in sub directories.
* Added a simple C++ example with Makefile.
* UPdated the readme with TF usage instructions.

Element types needed some reorganization to allow literals to know what kind of values to hold.