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
For example, I make a `MyFlashComponent` in my application and use the `$components` array to alias it to `Flash`. Currently the config key would need to be `Component.MyFlash`. I don't know if people would be expecting `Component.Flash` to work.