T-API: added 3-channels support to filters

```
check_regression=*OCL*BilateralFilter*:*OCL*BoxFilter*:*OCL*Blur*:*OCL*Filter2D*:*OCL*Median*:*OCL*Laplacian*
test_modules=imgproc
build_examples=OFF
test_filter=*OCL*BilateralFilter*:*OCL*BoxFilter*:*OCL*Blur*:*OCL*Filter2D*:*OCL*Median*:*OCL*Laplacian*
```
Added 3-channels support to:
* `cv::bilateralFilter`
* `cv::boxFilter`
* `cv::sqrBoxFitler`
* `cv::blur`
* `cv::filter2D`
* `cv::Laplacian`
* `cv::medianBlur`

Additional:
* eliminated restrictions `sdepth == ddepth` and `delta == 0` from `cv::filter2D`