Open inspector fullscreen and exploit monitor resolution, see #1474, #5591

- filecatalog.cc: add shortcuts
    'f' for image on full screen
    'Shift' 'f' for 100% crop on full screen
    (synchronization with mouse move as before with dual monitors)
- filepanel.cc: don't create inspector tab
- inspector.cc, inspector.h:
    create separate window for inspector
    scale image if requested
    exploit device scaling for full monitor resolution under macOS

rtgui/inspector.h

@@ -47,12 +47,15 @@ private:
     rtengine::Coord center;
     std::vector<InspectorBuffer*> images;
     InspectorBuffer* currImage;
-    double zoom;
+    bool scaled;
     bool active;
 
     sigc::connection delayconn;
     Glib::ustring next_image_path;
 
+    Gtk::Window window;
+    bool on_key_release(GdkEventKey *event);
+
     bool on_draw(const ::Cairo::RefPtr< Cairo::Context> &cr) override;
     void deleteBuffers();
 
@@ -62,6 +65,11 @@ public:
     Inspector();
     ~Inspector() override;
 
+    /** @brief Show or hide window
+     * @param scaled fit image into window
+     */
+    void showWindow(bool scaled);
+
     /** @brief Mouse movement to a new position
      * @param pos Location of the mouse, in percentage (i.e. [0;1] range) relative to the full size image ; -1,-1 == out of the image
      * @param transform H/V flip and coarse rotation transformation