3.0 Component, Behavior & Helper Configuration Improvement

With this approach it's also possible to configure Component, Behavoir & Helper in the app configuration. The configuration needs to look like the following:

```
'Component => [
    'Flash' => ['element' => 'Common.default']
]
```

Resolves https://github.com/cakephp/cakephp/issues/4296
I agree to @dereuromark, I think it's easier understandable for the user if the config and the alias of the component use the same name. This way you could also configure different aliases.