* Add CPU horizontal fusion pass for inception.

* Name change.

* Move horizontal fusion to cpu_fusion.

* Change horizontal fusion pass for inception to a general horizontal fusion pass.
Add a unit test conv_horizontal_fusion to cpu_fusion.

* Rename files.

* Correct cpu_fusion.hpp.

* Add NGRAPH_DEBUG.

* Set native layout when input format of slice is nChw16c or nChw8c and lower bound of
channels is not a multiple of 16 or 8.