[FrameworkBundle] Improving bad bundle exception in _controller

...ntroller in a routeHi guys!

This improves the exception message when you use a bad bundle name in the `_controller` syntax in a routing file. Here is the before and after of the message with this mistake (real bundle is `KnpUniversityBundle`):

```yaml
some_route:
    pattern:  /
    defaults: { _controller: "Knp2UniversityBundle:Course:index" }
```

![screen shot 2014-06-23 at 9 27 55 pm](https://cloud.githubusercontent.com/assets/121003/3367065/448e8298-fb54-11e3-92ea-9bf04510cb6d.png)

![screen shot 2014-06-23 at 9 48 14 pm](https://cloud.githubusercontent.com/assets/121003/3367063/3c79cf36-fb54-11e3-87c4-29428248ee47.png)

Notice the before and after behavior is the same `InvalidArgumentException` (just a different message).

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

Catching the plain `InvalidArgumentException` from `Kernel::getBundles()` seems a bit "loose". Should we consider creating a new exception (e.g. `BundleDoesNotExistException`) that extends `InvalidArgumentException` and throw it from inside `Kernel::getBundles`? This would allow us to catch more precisely, and it seems like it would be BC.

Suggestions and thoughts warmly welcome!

Thanks!