add softmax op and documentation

* one output

multiple outputs

initial clean-up

* test clean-up

current version

test pass

* clean up

* fix format

* add dbeta,dgamma asserts

* revert some files

* 0644 on node.cpp

* 0644 on mkldnn_utils.cpp

* 0644 on more files

* add support for serialization + test case

* fix merge errors

* Add aliased Constants to aliased_output test.

* add support for const as outputs

Cyphers/dochow

* named uniquely

* rename get_name methods

* add unit test for function name

* add node name unit test

* make unique name const

Merge branch 'cyphers/dochow' of https://github.com/NervanaSystems/private-ngraph-cpp into cyphers/dochow

This function has been removed in favor of `project`, but as @adstraw discovered, its prototype was still lying around the header file, lookin' all smug.

CPU: Remove local function_name again

Jmenon/port

* add unit test for resource deallocation

fix leak

* cleanup

* Remove NGRAPH_DISTRIBUTED from allreduce op class
* Add allreduce doc

* fix bug and enable some tests

* eliminate duplicated code, change some parameter names

* Exit build with error message when NGRAPH_USE_PREBUILT_LLVM is requested on non-Linux OSes

This fixes the previously broken compilation of ngraph-mxnet which directly utilized serializer.hpp

* add support for both command line arg and env var to set NGRAPH_WARINGS_AS_ERRORS'