added 3 channels support to cv::bilateralFilter

Conflicts:
	modules/imgproc/test/ocl/test_filters.cpp
added 3-channels support to cv::boxFilter, cv::blur, cv::sqrBoxFilter
added 3-channels support to cv::filter2D, cv::Laplacian
added 3-channels support to cv::medianBlur
refactored filter2D; eliminated restrictions sdepth == ddepth, delta == 0
added perf test for CalcBackProj
Merge branch 'master' of https://github.com/Itseez/opencv into back_proj_fix
FEATURES2D: add DenseFeatureDetector Python wrapper
UMat map-unmap synchronization test
Merge pull request #2523 from ilya-lavrenov:tapi_filters
changed type of sanity check
added jpeg progressive support.
Fixed stereoBM for Intel CPU.
Merge pull request #2378 from ngryman:progressive_jpeg
Merge pull request #2478 from clemenscorny:master
improved cv::filter2D
Merge pull request #2528 from mlyashko:back_proj_fix
Merge pull request #2529 from ilya-lavrenov:tapi_filter2D
Merge pull request #2505 from alalek:umat_unmap_synchronization_test
UMat: issue in OpenCLAllocator::unmap()