[WIP] Editing relations

[bobdenotter]

Fixes #330. Fixes #329.

[bobdenotter]

When editing + saving a record, I get the following exception:

If I comment out the two lines that modify the relations, it works as before (minus persisting the changed relations, obviously..

        // Remove old ones
        foreach ($currentRelations as $currentRelation) {
            // $this->em->remove($currentRelation);
        }

        // Then (re-) add selected ones
        foreach ($relation as $id) {
            …
            // $this->em->persist($relation);
        }

[JarJak]

@bobdenotter I suppose this is a bug in Gedmo. For some reason Sortable conflicts with Translatable here, even if Relation is not a translatable entity.