Implementation of PCT signature extractor (position-color-texture) and evaluation of their Signature Quadratic Form Distance (SQFD).

Minor clean up. There was no need to keep these lines.

- with big images the int multiplication can overflow

Changed statements of type "#if __CUDA_ARCH__ >= 200" to
"#if defined __CUDA_ARCH__ && __CUDA_ARCH__ >= 200" in order to
avoid warnings about __CUDA_ARCH__ being undefined.

- Saliency stl array instead of pointer array added
- Perf test in Extra Repository
- Epsilon change to 10E-3

This was already fixed here:
https://github.com/patricksnape/opencv_contrib/commit/8247a7a0f59ba6c1fcfbac6a660db3f8acdc9ff8

Now uses cvround

round does not exist in MSVC<2012 - added with the same code
as in line_descritor/binary_descriptor.cpp

vs2010 breaks

fixed several warnings in opencv_contrib (text, xfeatures2d); added tesseract installation mini-guide in text/readme.md