optimized sep filter
simplified cv::sepFilter2D OpenCL part
generalized OpenCL version of cv::sepFilter2D; removed some restrictions and added 3-channels support
enabled 3-channels support for cv::createSuperResolution_BTVL1
changed epsilon for test pass on Win32
added 3-channels support to optimized version
changing default perf strategy from BASIC (old) to SIMPLE (new, faster)
Merge pull request #2503 from mlyashko:optflow_dualtvl1
Merge pull request #2491 from ilya-lavrenov:tapi_sep_filter
Merge pull request #2515 from apavlenko:perf_default_strategy
Merge branch 'master' of https://github.com/Itseez/opencv into 3.x