TbNavBar positioning error

I believe the order of parameter checking in order to decide if the navbar should be static or not is wrong!

Right now the code:
* First checks the position of the bar (POSITION_TOP or POSITION_BOTTOM) 
* and then checks to see if the bar should be static.

Since the position is always either POSITION_TOP or POSITION_BOTTOM then the bar will always appear as fixed.

In this pull request, the order of checks is changed.

so you can use something like:

```php
<?php $this->widget('bootstrap.widgets.TbNavbar',array(
    'collapse'=>false,
    'htmlOptions' => array(
        'static' => true,
    ),
    ...
```

in order to have a navigation bar appear as static.