Bug 5774 Unpredicatable behaviour on double click in packages view
from EC: If you double click a file in the packages view, it opens the file (technically, compilation unit I believe) -- if not already open. However, if the file is already open, a single click selects it as the active editor tag; a double click expands its structure in the packages view. This is unpredictable behavior ;
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
fViewer.setUseHashlookup(true);
		fViewer.addFilter(fPatternFilter);
		fViewer.addFilter(fLibraryFilter);
		
		fViewer.addFilter(fWorkingSetFilter);
		if(fMemento != null) 
			restoreFilters();
		else
			initFilterFromPreferences();
			
		
		
		fViewer.setInput(findInputElement());
		initDragAndDrop();
		initFrameList();
		initKeyListener();
		updateTitle();
		
		MenuManager menuMgr= new MenuManager("#PopupMenu"); 
		menuMgr.setRemoveAllWhenShown(true);
		menuMgr.addMenuListener(this);
		fContextMenu= menuMgr.createContextMenu(fViewer.getTree());
		fViewer.getTree().setMenu(fContextMenu);
		getSite().registerContextMenu(menuMgr, fViewer);
		
		makeActions(); 
			
		fSelectionListener= new ISelectionChangedListener() {
			public void selectionChanged(SelectionChangedEvent event) {
				handleSelectionChanged(event);