Several \yii\bootstrap\NavBar fixes

- links to bootstrap site was actualized
- `padded` renamed to `renderInnerContainer` to be consistent with other "do-something" boolean options
- `innerContainerOptions` added which very important for custom bootstrap assemblies
- special `tag` attribute now recognized inside options, this is very important to get correct html5 markup in several cases. For example if you want make navigation bar as header with role banner like on bootstrap site
- `collapseOptions` added, this is very important to get correct html5 markup in several cases. For example if you want make inner navigation as nav with role navigation like on bootstrap site
- overall refactoring

Why the hell all this needed? :) All simple here is example:

```php
NavBar::begin([
    'brandLabel' => 'Company label here',
    'options' => ['tag' => 'header', 'role' => 'banner'],
    'collapseOptions' => ['tag' => 'nav', 'role' => 'navigation'],
    'innerContainerOptions' => ['class' => 'container-16'], // this is highly often used while you use bootstrap as framework and have more than 1 grid system
]);
...
NavBar::end();
```