Shift TimelineView’s items half a day

They are supposed to show how many _nigths_ guests are staying in
lodgins, thus they arrive at afternoon and leave at morning; the shift
puts the starting position at midday.

src/timelineview.cpp

@@ -9,7 +9,7 @@ struct TimelineView::Item
         , day(day)
     {
         item->setParentItem(&view);
-        item->setPosition(QPointF(day * view.dayWidth(), 0.0));
+        item->setPosition(QPointF(day * view.dayWidth() + view.dayWidth() / 2, 0.0));
         item->setSize(QSizeF(len * view.dayWidth(), view.height()));
         item->setVisible(true);
     }