Adapted the cross size to rulers

src/board/UBBoardController.cpp

@@ -108,6 +108,8 @@ UBBoardController::UBBoardController(UBMainWindow* mainWindow)
     mPenColorOnLightBackground = UBSettings::settings()->penColors(false).at(penColorIndex);
     mMarkerColorOnDarkBackground = UBSettings::settings()->markerColors(true).at(markerColorIndex);
     mMarkerColorOnLightBackground = UBSettings::settings()->markerColors(false).at(markerColorIndex);
+
+    UBSettings::settings()->crossSize = UBGeometryUtils::millimetersPerCentimeter * 4;
 }