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'

* make json lib an external project
* add env var to turn warnings to errors

* Improve the readability of imported doxygenclass api doc style
from being so small (WIP).

Also fixed the not op to not import abs doxygenclass.

* Make sure no large files get added to git

* Other doxygen files to exclude from git

* WIP phase two styling code to save and test

* Cleanup for PR

Fix bugs and enable dot in GPU