Bug 172000 [Wizards] WizardNewFileCreationPage should support overwriting existing resources
In the WizardNewFileCreationPage, there should be a method to set allowExistingResources flag for ResourceAndContainerGroup member. It is useful when both "create" and "renew/overwrite" operations are meaningful for a wizard.
bundles/org.eclipse.ui.ide/extensions/org/eclipse/ui/dialogs/WizardNewFileCreationPage.java
private static final int SIZING_CONTAINER_GROUP_HEIGHT = 250;
	
	private IStructuredSelection currentSelection;
	
	private IFile newFile;
	private URI linkTargetPath;
	
	private ResourceAndContainerGroup resourceGroup;
	private Button advancedButton;
	private CreateLinkedResourceGroup linkedResourceGroup;
	private Composite linkedResourceParent;
	private Composite linkedResourceComposite;
	
	private String initialFileName;
	
	/**
	 * The file extension to use for this page's file name field when
	 * it does not exist yet.
	 * @see WizardNewFileCreationPage#setFileExtension(String)
	 * @since 3.3
	 */
	private String initialFileExtension;
	private IPath initialContainerFullPath;
	/**
	 * Height of the "advanced" linked resource group. Set when the advanced
	 * group is first made visible.
	 */
	private int linkedResourceGroupHeight = -1;
	/**