Bug 25845 Support for manually attaching source to a class path container
From Dejan: There is a work item on the ability to manually attach source to classpath entries managed by classpath container. We discussed it and we have workable options but we would like if we can have it by M3 because we want to start self-hosting using classpath containers ourselves.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/LibrariesWorkbookPage.java
private final Object[] EMPTY_ARR= new Object[0];
		
		
		public void customButtonPressed(TreeListDialogField field, int index) {
			libaryPageCustomButtonPressed(field, index);
		}
		
		public void selectionChanged(TreeListDialogField field) {
			libaryPageSelectionChanged(field);
		}
		
		public void doubleClicked(TreeListDialogField field) {
			libaryPageDoubleClicked(field);
		}
		public Object[] getChildren(TreeListDialogField field, Object element) {
			if (element instanceof CPListElement) {
				return ((CPListElement) element).getChildren(false);
			}
			return EMPTY_ARR;
		}
		public Object getParent(TreeListDialogField field, Object element) {
			if (element instanceof CPListElementAttribute) {
				return ((CPListElementAttribute) element).getParent();
			}
			return null;
		}
		public boolean hasChildren(TreeListDialogField field, Object element) {
			return (element instanceof CPListElement);