0031570: Samples - add Qt samples similar to standard MFC samples

Added Qt sample OCCTOverview providing examples of use of OCCT API with relevant code and demonstration of results in the viewer.

Off-topic: some unused images are removed from dox/introduction/images/

samples/qt/OCCTOverview/src/TranslateDialog.h

@@ -0,0 +1,56 @@
+// Copyright (c) 2020 OPEN CASCADE SAS
+//
+// This file is part of the examples of the Open CASCADE Technology software library.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE
+
+#ifndef TRANSLATEDIALOG_H
+#define TRANSLATEDIALOG_H
+
+#include <Standard_WarningsDisable.hxx>
+#include <QComboBox>
+#include <QFileDialog>
+#include <QList>
+#include <QListView>
+#include <QShowEvent>
+#include <QWidget>
+#include <Standard_WarningsRestore.hxx>
+
+//! Qt file dialog for save and restore sample files
+class TranslateDialog : public QFileDialog
+{
+public:
+  TranslateDialog(QWidget* = 0, Qt::WindowFlags flags = 0, bool = true);
+  ~TranslateDialog();
+  int                   getMode() const;
+  void                  setMode(const int);
+  void                  addMode(const int, const QString&);
+  void                  clear();
+
+protected:
+  void                  showEvent(QShowEvent* event);
+
+private:
+  QListView*            findListView(const QObjectList&);
+
+private:
+  QComboBox*            myBox;
+  QList<int>            myList;
+};
+
+#endif // TRANSLATEDIALOG_H