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/dialogs/ProjectContentsLocationArea.java
/**
	 * Check if the entry in the widget location is valid. If it is valid return
	 * null. Otherwise return a string that indicates the problem.
	 * 
	 * @return String
	 */
	public String checkValidLocation() {
		
		String locationFieldContents = locationPathField.getText();
		if (locationFieldContents.length() == 0) {
			return IDEWorkbenchMessages.WizardNewProjectCreationPage_projectLocationEmpty;
		}
		URI newPath = getProjectLocationURI();
		if (newPath == null) {
			return IDEWorkbenchMessages.ProjectLocationSelectionDialog_locationError;
		}
		
		if (existingProject == null && isDefault()) {
			return IDEWorkbenchMessages.WizardNewProjectCreationPage_projectNameEmpty;
		}
		
		IStatus locationStatus = ResourcesPlugin.getWorkspace()
				.validateProjectLocationURI(existingProject,
						isDefault() ? null : newPath);
		if (!locationStatus.isOK()) {
			return locationStatus.getMessage();
		}
		if (existingProject != null) {
			URI projectPath = existingProject.getLocationURI();
			if (projectPath != null && URIUtil.equals(projectPath, newPath)) {