Inform LocationFilterModel of changed dive site name

Since commit 01d961086c, the location filter
list is updated if a dive site is edited. The problem is that if the
name of a selected dive site is changed, the selection is lost.

Therefore, before repopulating, inform the location filter that a dive
site changed its name. The location filter then internally changes the
name and can properly transfer the old selection on repopulate. This is
performed via the new LocationInformationWidget::nameChanged signal,
which is connected to the new LocationFilterModel::changeName slot.

A special case to be handled is the following:
 [ ] Site 1
 [x] Site 2
and "Site 2" being renamed to "Site 1", i.e. both sites being merged.
Here, the merging is detected and "Site 1" will likewise be checked:
 [x] Site 1
 [x] Site 1
No merging is performed, as the list will be repopulated anyway.

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

desktop-widgets/locationinformation.h

@@ -41,6 +41,7 @@ signals:
 	void stopFilterDiveSite();
 	void requestCoordinates();
 	void endRequestCoordinates();
+	void nameChanged(const QString &oldName, const QString &newName);
 
 private:
 	void clearLabels();