turn on testing support in root binary directory
rewrite add_test command for accuracy tests:

* use new syntax introduced in CMake 2.8.0
* set OPENCV_TEST_DATA_PATH enviroment property
disable CTest target for opencv_test_viz:

opencv_test_viz creates windows and waits until user close them,
it is not appropriate for automatic testing
add CTest targets for sanity tests
determine test category (Public vs Extra) based on module location
Merge pull request #3356 from jet47:ctest-support