Big config refactoring

This time, I added the real Xml and Yaml FileLoaders (will be moved to Testing component tonight). This resulted in some errors when using XML: symfony/symfony#8630

This PR fixes all those errors and with that, it also refactored the complete navigation:
- added a `route_stacks/route_stack` node to `content_path`
- put options in `options`

This will also help to move to the config suggested by @dantleech: https://github.com/symfony-cmf/RoutingAutoBundle/pull/35#issuecomment-27682303

To see how the current XML and Yaml config files look, take a look at the files.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | tbd