Dive site: add edit field to dive site table

Add an edit column that calls the new editDiveSite() function
of MainWindow. The calling code is in DiveSiteSortedModel.
Quite illogical, but that's how TableView works, for now.

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

desktop-widgets/mainwindow.h

@@ -82,6 +82,7 @@ public:
 	void enableDisableOtherDCsActions();
 	void enterEditState();
 	void exitEditState();
+	void editDiveSite(dive_site *ds);
 
 	MainTab *mainTab;
 	PlannerDetails *plannerDetails;