* Refactor auto-detection of parallel frameworks
* Implement cv:getNumThreads, cv::setNumThreads and cv::getThreadNum for all supported frameworks
* From now cv::setNumThreads(0) can be used to turn off parallelisation

+ Some minor formatting fixes.

fixed possibly inccorrect interval measurements in flann's timer (bug #1165). Note: this may break binary compatibility, but since the class is not wrapped in Java and not exposed in Windows API, for example (it's considered internal-use class for flann), the effect should be minimal

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

Replaced SVN instructions with Git ones for 'Installation in Windows' section (Issue #2249); Also, fixed both bugs from issue #2374 in the same section.