Make Otsu and Triangle algorithms mutually exclusive in cv::threshold code.
Signed-off-by: Miroslav Benes <mbenes@suse.cz>

Add Triangle method for automatic threshold computation next to the existing
Otsu's method. Triangle deals better with images whose histogram does not
contain dominant peak.

See paper Zack GW, Rogers WE, Latt SA.: Automatic measurement of sister
chromatid exchange frequency. J Histochem Cytochem. 1977 Jul;25(7):741-53.

IPP can be switched on and off on runtime;

Optional implementation collector was added (switched off by default in CMake). Gathers data of implementation used in functions and report this info through performance TS;

TS modifications for implementations control;

1. someMatrix.data -> someMatrix.prt()
2. someMatrix.data + someMatrix.step * lineIndex -> someMatrix.ptr( lineIndex )
3. (SomeType*) someMatrix.data -> someMatrix.ptr<SomeType>()
4. someMatrix.data -> !someMatrix.empty() ( or !someMatrix.data -> someMatrix.empty() ) in logical expressions

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()).