have admin extension handle the locale

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | travis
| Fixed tickets | #161
| License       | MIT
| Doc PR        | TODO

So yes, this re-introduces the optional dependency with CoreBundle. But that is ok its just for the phpcr-odm document and the dependency on phpcr-odm itself is also optional.