* reduce fprop cache outputs

* refactor traverse nodes

* Slight refactor, add test, adress PR comments

* fix formatting

* get_subgraph_outputs

* simplify the condition

* 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

* remove deprecated

* remove all legacy Backend API usage

remove deprecated files

* pull in changes from master

* fix GPU calls

* disable tests in convolution generator

* update per PR comments. Enable performance counter feature.

* update per PR comments

* fix build error

* fix conditionally compiled test :(

* force backend compile() to make a copy of the graph

fix copy_with_new_args on ops that have function pointers internal

update unit test for new backend API

add unit test for multiple simulataneous backends

* move get_subdevices virtual method to Manager class

* update GPU to latest

* update call methods

* add remove_compiled_function()

* cleanup

* cleanup

* fix all headers to be standalone as far as includes go

* include cleanup

* cleanup includes

* cleanup

* include tester

* wip

* cleanup

* cleanup

* cleanup

* Replace using aliases with actual classes

* fix Shape declarations

fix clone of function with multiple outputs

* wip

* wip

* remove get_vector from runtime::TensorView class as it was for unit test only

* cleanup

* move writting vector to runtime::TensorView to the unit test dir

* merge fix

* PR review change

* update from PR comment

* update changes file

* recreate ops

* style

* recompute ops

* style

* fix

* recreate ops

* style

* recompute ops

* style

* fix

* some

* more

* style

* remove a line

* const

* style

* NodeMap was using non-standard operator[] behavior.

* Missing include

* Function can have multiple results
Remove external use of ValueType, TupleType, Tuple
Remove many external uses of Output and Input

* corresponding CPU backend changes

* Update master changes.

* Remove type arg from Function, add changes.md

* Merge changes.

* Move bodies to .cpp, add brief doc

* Merge CPU changes.

* Remove xla includes from non-xla files

* Remove xla from tests

* First part of xla tuple support

* change fprop_cache to assume multi-output bprop functions

* New wrappers for handling tuples with XLA

* Review comments

* remove old xla files

* fix merge errors

* hand edit models to use multi output instead of tuples

* in progress

* working cache_fprop, no tests

* style fix

* all inputs to bprop (except adjoints) are cached from fprop

* fix typos, make sure to check count == 0

* fix code format

* remove ngvm

* remove NGVM from cmake

* remove ParameterizedConstant
* use simpler element Type definition
* Move TraitedType to NGVM directory

* used something other than aligned_alloc for mac

* Fix compile error for aligned_free on Mac

topological sort pass to call the utility function
clone util to be used by frameworks e.g. for fprop cache

* add support for n-dimensional operations by calling runtime/kernels

* rename cpu backend classes and files

* add tuple support to INTERPRETER

* move ndarray out of runtime to test where it belonged

* fix Tuple op per review comment

* add json lib 2.1.1

* add json serialization of graph

* cleanup

* enhance unit test

* remove FunctionProvider class and replace with virtual get_function() in Node

* remove json code from element_type

* move serialize to be directly in the ngraph namespace. cleanup header file.

* add cname check to element::operator==

* add using json = nlohmann::json

* ParameterizedTensorView and ElementType cleanup

* change element to_type() to from()

* wip

* remove ndarray dependency from ParameterizedTensorView

* get rid of operator= on ParameterizedTensorView

* remove unimplemented ctor

* remove get_parameterized_tensor_view from TensorView class

* cleanup

* the patient will get worse before getting better. remove ParameterizedTensorView from element type

* cleanup obsolete includes

* remove unused file

* move aligned_buffer and cleanup

* cleanup

* wip

* wip

* wip

* cleanup

* cleanup

* wip

* finally got rid of getting a non-const vector from PTV

* wips

* wip

* remove unused

* fix PR comments

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