* Custom deep learning layers support

* Stack custom deep learning layers

Enable FP16 GPU target for DL Inference Engine backend.

include relu6 ocl kernel and layer fusion support
Signed-off-by: Li Peng <peng.li@intel.com>

Found via `codespell`

* Added the imagesFromBlob method to the dnn module.

* Rewritten imagesFromBlob based on first dkurt comments

* Updated code with getPlane()

* Modify comment of imagesFromBlob() in dnn module

* modified comments, removed useless assertions & added OutputArrayOfArray

* replaced tabs with whitespaces & put vectorOfChannels instantiation outside the loop

* Changed pre-commit.sample to pre-commit in .git/hooks/

* Added a test for imagesFromBlob in test_misc.cpp (dnn)

* Changed nbOfImages, robustified test with cv::randu, modified assertion

* Intel Inference Engine deep learning backend.

* OpenFace network using Inference Engine backend

It allows umat buffers used in net forward interface
Signed-off-by: Li Peng <peng.li@intel.com>

add a corresponding test

Add layer forward interface with InputArrayOfArrays and
OutputArrayOfArrays parameters, it allows UMat buffer to be
processed and transferred in the layers.
Signed-off-by: Li Peng <peng.li@intel.com>