Support MKL2017 DNN API

[yiheng]

Intel MKL release 2017 version and it contains a DNN API, which provide DNN operation optimized for IA architecture. We will add new layers which leverage these new APIs to get a better performance on CPU.

[bhack]

Can Intel finally clarify relation roadmap against this and #363? At "marketing" level is quite confusional.

[i8run]

#363 is the same as this issue. @bhack

[bhack]

But is mkl-dnn https://github.com/01org/mkl-dnn?

[jason-dai]

Here mkl-dnn actually refers to the DNN primitives in Intel MKL 2017 (https://software.intel.com/en-us/articles/introducing-dnn-primitives-in-intelr-mkl)