OCL: matchTemplate - added support for 3-channels and optimization

**Description:**
* added support for 3-channels for all methods
* changed  kernels for `CCOEFF` and `CCOEFF_NORMED`
* for `CCORR` added implementation using `dft`, called when the `template size >= 18`
* for `SQDIFF` added implementation using `CCORR`, called when `template size >= 18`
* for `CCORR` cn==1 used vector data types (`int4` and `float4` instead of `int` and `float`)

**Performance report:**
http://ocl.itseez.com/intel/export/perf/pr/2786/report/

check_regression=*OCL*MatchTemplate*
test_modules=imgproc
build_examples=OFF
fixed