filter: on show focus on fulltext-field

After pressing CTRL-F let the user immediately enter a search
string.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

desktop-widgets/filterwidget2.cpp

@@ -264,6 +264,7 @@ void FilterWidget2::updatePlanned(int value)
 void FilterWidget2::showEvent(QShowEvent *event)
 {
 	QWidget::showEvent(event);
+	ui.fullText->setFocus();
 	filterDataChanged(filterData);
 }