Add IPP support in cvtColor function
Adding read/write functions to PCA class. Update PCA test.
Fix a bug of retinaParameters.
When colorMode is set to 0 via Retina::_init method, _retinaParameters's
colorMode variable is not correctly assigned.
Added MOG and MOG2.
Resolved a compiling error under Linux.
Resolved a compiling warning under Windows.
Resolved compiling errors under Linux.
Used perf_precomp.hpp instead of precomp.hpp for test.
macros -> template in IPP support cvtColor
Merge pull request #4 from Itseez/2.4

OpenCV changes
Fix bilateralFilter function
Optimized mog and mog2, which have much better performance.
Make some tweaks to make `sum` operations less frequently
Fix build error.
Remove trailing whitespace.
gpu TVL1 Optical Flow optimization:

do not calculate sum of error in every round of iteration;
instead the error will be summed every 2nd times or more, 
if the previous sum of error is too far away from threshold.
Merge pull request #1346 from jet47:gpu-tvl1-optimization
Restored one executable bit that was lost during the war on whitespace.
appended ocl::finish to test_cycle defines
rewrite gpu stereo multi gpu sample:

* use different approaches -> threads and streams
* clean up code