move document to model

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | yes
| BC breaks?    | yes
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | TODO (small adjustments due to deprecation)

This turned out quite a big change in terms of code. in terms of deprecation, the only change for the user is he should now use Doctrine\Phpcr\Route instead of Document\Route.

SimpleCmsBundle will need adjustments as i did not do BC classes for the route and content providers.

Note that i did not yet change the configuration in a way that lets us chose the storage layer - that will be the next step when porting the things from #95 to this new concept.