added recommended number of stripes to parallel_for_, modified some of the functions to use larger stripes (for better performance)

expanded cv::threshold parallelization to other threading frameworks; fixed potential bug with unprocessed bottom of the image; fixed build problem in stitching

minor build system changes (now cuda code in opencv_core is compiled using CUDA_ARCH* cmake variables)

Added threaded versions (enabled only for Tegra at the moment) of threshold, erode/dilate. Slighlty restructured the code of medianBlur.

replaced "const InputArray&" => "InputArray"; made InputArray and OutputArray references. added "None()" constant (no array()).

a big patch; use special proxy types (Input/OutputArray, Input/OutputArrayOfArrays) for passing in vectors, matrices etc.