Implement the context menu a different way

It seems that this is the way this is supposed to be done - instead of
manually looking at what kind of click we get, Qt decides when to create
a context menu for us - this way things like the Windows Menu button
will work automagically.

As an example I also implemented the "remove dive from trip"
functionality, which exposes some other bugs (like the fact that the
dive that isn't part of a trip ends up being sorted at the very end of
the dive list).

This commit contains a "testSlot" implementation to remind me how to
figure out which dive / trip we are on.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/divelistview.h

@@ -28,21 +28,25 @@ public:
 	bool eventFilter(QObject* , QEvent* );
 	void unselectDives();
 	void selectDive(struct dive *, bool scrollto = false);
-	void mousePressEvent(QMouseEvent *event);
+	void contextMenuEvent(QContextMenuEvent *event);
 
 public slots:
 	void toggleColumnVisibilityByIndex();
 	void reloadHeaderActions();
 	void headerClicked(int);
 	void showSearchEdit();
+	void removeFromTrip();
+	void testSlot();
 
 Q_SIGNALS:
 	void currentDiveChanged(int divenr);
+
 private:
 	bool mouseClickSelection;
 	int currentHeaderClicked;
 	DiveTripModel::Layout currentLayout;
 	QLineEdit *searchBox;
+	QModelIndex contextMenuIndex;
 };
 
 #endif // DIVELISTVIEW_H