[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!

this does not actually test the new feature. You need to test the message