added cmake error and flag to override in case unsupported Qt 5.8.0 is
used on windows if the flag USE_UNSUPPORTED_QT is set, only a warning is displayed, otherwise a fatal error
Please merge https://www.graphics.rwth-aachen.de:9000/OpenFlipper-Free/OpenFlipper/merge_requests/29 first, and update the OpenFlipper submodule on this branch, since the root CMakeLists.txt is modified
closes #101 (closed)