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
* Sets the value of this page's file name field, or stores it for future
	 * use if this page's controls do not exist yet.
	 * 
	 * @param value
	 *            new file name
	 */
	public void setFileName(String value) {
		if (resourceGroup == null) {
			initialFileName = value;
		} else {
			resourceGroup.setResource(value);
		}
	}
	/**
	 * Set the only file extension allowed for this page's file name field.
	 * If this page's controls do not exist yet, store it for future use.
	 * <br><br>
	 * If a file extension is specified, then it will always be 
	 * appended with a '.' to the text from the file name field for 
	 * validation when the following conditions are met:
	 * <br><br>
	 * (1) File extension length is greater than 0
	 * <br>
	 * (2) File name field text length is greater than 0
	 * <br>
	 * (3) File name field text does not already end with a '.' and the file 
	 *     extension specified (case sensitive)
	 * <br><br>
	 * The file extension will not be reflected in the actual file
	 * name field until the file name field loses focus.