* adding group convolution implementation for plaidml

* update CMakeLists.txt to include new group convolution files

* adding new ngraph unit tests for grouped convolutions

* adding group conv unit test back in for plaidml backend

* specify group convolution support in plaidml

* add denise as codeowner for plaidml runtime dir

* remove commented-out lines of unit test manifest

* style changes

* resolve all discussions in PR

* skip data dilation unit test on cpu backend