DoctrineORMFieldGuesser - ManyToMany relations

The `multiple` formOption is now set to `true` in the case of a ManyToMany Entity relation
Merge pull request #676 from mguillermin/many-to-many-field-guesser

DoctrineORMFieldGuesser - ManyToMany relations
Fixing missing import
Merge pull request #677 from mguillermin/many-to-many-field-guesser

Fixing error in PR #676
Update german translation
Merge pull request #678 from fadoe/master

Update german translation
Update readme for grec translation