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/src/org/eclipse/ui/internal/ide/misc/ResourceAndContainerGroup.java
* The name will include the resource extension if the 
	 * preconditions are met.
	 * @see ResourceAndContainerGroup#setResourceExtension(String)
	 *  
     * @return The resource name
     * @since 3.3
     */
    public String getResource() {
    	String resource = resourceNameField.getText();
    	if (useResourceExtension()) {
    		return resource + '.' + resourceExtension;
    	}
        return resource;
    }
    
    /**
	 * Returns the resource extension.
	 * 
	 * @return The resource extension or <code>null</code>.
	 * @see ResourceAndContainerGroup#setResourceExtension(String)
	 * @since 3.3 
     */
    public String getResourceExtension() {
    	return resourceExtension;
    }
    
    /**
     * Determines whether the resource extension should be added to the 
     * resource name field.
     * <br><br>