Updating OpenFace to version 2.2.0 (#741)

Change log:

Moving to C++17. This means that the code can only be build using C++17 compilers (e.g. g++ >8 and Visual Studio 2017, clang > 5), fixing related bugs - (#698, #629, #641)
Removing an explicit dependency on boost (all the filesystem operations are performed using std::filesystem or boost::filesysteme). If boost is available it will used boost:filesystem, otherwise std::filesystem (this requires C++17)
Visual Studio 2017 is now the main version for Visual Studio builds, VS 2015 is no longer supported
Updating OpenCV to 4.1 version (#511)
Fixing a bug with output images when using GUI (#694)
Updating RAWImage - #609, so it can be initialized from System.Drawing.Bitmap directly
Fixing overlap detection for multi face tracking (#693)

lib/3rdParty/OpenCV/include/opencv2/gapi/util/compiler_hints.hpp

@@ -0,0 +1,19 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+//
+// Copyright (C) 2018 Intel Corporation
+
+#ifndef OPENCV_GAPI_UTIL_COMPILER_HINTS_HPP
+#define OPENCV_GAPI_UTIL_COMPILER_HINTS_HPP
+
+namespace cv
+{
+namespace util
+{
+    //! Utility template function to prevent "unused" warnings by various compilers.
+    template<typename T> void suppress_unused_warning( const T& ) {}
+} // namespace util
+} // namespace cv
+
+#endif /* OPENCV_GAPI_UTIL_COMPILER_HINTS_HPP */