This reverts commit 94b97b7a.

This reverts commit 9b8c4739.

This reverts commit 618fbf55.

This reverts commit a8c5e356.

Conflicts:
	modules/imgproc/src/imgwarp.cpp

* 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.