OCL: matchTemplate: optimization

Merge after: https://github.com/Itseez/opencv/pull/2849

**Description:**
* changed  kernels for `CCOEFF` and `CCOEFF_NORMED`
* for `CCORR` and `SQDIFF` added implementation using `dft`, called for template size >= 18 
* for `CCORR` cn==1 used vector data types (`int4` and `float4` instead of `int` and `float`)
* used `float` instead of `int` for `CV_8U`

**Performance report:**
http://ocl.itseez.com/intel/export/perf/pr/2786/report/

check_regression=*OCL*MatchTemplate*
test_modules=imgproc
build_examples=OFF