change keyboard shortcuts; update tooltips

- "Load Track as Route" is now triggered by pressing `Shift-O`
- "Load No-Go-Areas" is now triggered by pressing `Shift-N`
- tooltip for navbar link is updated an ready for translation

js/plugin/NogoAreas.js

@@ -5,6 +5,7 @@ BR.NogoAreas = L.Control.extend({
                 enable: 78, // char code for 'n'
                 disable: 27, // char code for 'ESC'
             },
+            import: 78, // char code for 'n'; used in conjunction with 'shift'
         },
     },
 
@@ -147,6 +148,13 @@ BR.NogoAreas = L.Control.extend({
         if (!BR.Util.keyboardShortcutsAllowed(e)) {
             return;
         }
+
+        if (true === e.shiftKey && e.keyCode === this.options.shortcut.import) {
+            $('#loadNogos').modal('show');
+
+            return;
+        }
+
         if (e.keyCode === this.options.shortcut.draw.disable && this.button.state() === BR.NogoAreas.STATE_CANCEL) {
             this.stopDrawing(this.button);
         } else if (