Re-add inspector tab as an option (#5867)

- add option "inspectorWindow" to switch from tab to fullscreen view
- add option "zoomOnScroll" to configure scroll device for zoom or pan
- add both options to preferences
- filepanel creates tab if not inspectorWindow
- inspector adapts to settings inspectorWindow and zoomOnScroll
- filebrowser shows context menu item for inspector only if inspectorWindow

rtgui/options.h

@@ -289,6 +289,8 @@ public:
     bool internalThumbIfUntouched;
     bool overwriteOutputFile;
     int complexity;
+    bool inspectorWindow; // open inspector in spearate window
+    bool zoomOnScroll;    // translate scroll events to zoom
 
     std::vector<double> thumbnailZoomRatios;
     bool overlayedFileNames;