* core(logger): add CV_LOG_ONCE_xxx() CV_LOG_IF_xxx() macros

* core(logger): keep tests disabled

* imgproc(integral): avoid OOB access

* imgproc(test): fix integral perf check

- FP32 computation is not accurate

* imgproc(integral): tune loop limits

Use argument value for 'mat' in call to format for vector_mat and vector_mat_template

* Supported Div op for constants

* Added Mul test

The hard-coded string value "Mat" was used in the two format strings for vector_mat and vector_mat_template, preventing UMat arguments to functions that have these types from working correctly. as noted in #12231.

core: fix MatExpr::size() for gemm()

* core(test): MatExpr::size() test for gemm()

* core: fix MatExpr::size() for gemm()

cuda4dnn(activations, eltwise, scale_shift): refactor to reduce code duplication

* refactor activations

* refactor eltwise kernels

* move all functors to functors.hpp

* remove bias1 and scale1 kernels

* Ignore clang warnings for deprecated enum+enum operations in mat.inl.hpp

* build: added customization macros, cmake flags for OpenCV build

V4L2: Add V4L2_PIX_FMT_Y12 (12 bit grey) support

* Vectorize calculating integral for line for single and multiple channels

* Single vector processing for 4-channels - 25-30% faster

* Single vector processing for 4-channels - 25-30% faster

* Fixed AVX512 code for 4 channels

* Disable 3 channel 8UC1 to 32S for SSE2 and SSE3 (slower).  Use new version of 8UC1 to 64F for AVX512.

in sample codes instead of cpp files' name.

removed all the changes occured while trying to resolve conflicts