Constraint: Presence of translations for publications #109
Description
It should be checked that all places, where translations are wanted, check for the presence of translations for all languages its publication is available in.
An example: An entry provides a translation in German. If then the publication it is available in gets an English version (an English translation is added to the publication instance), it should report an error for the entry unless a corresponding English translation is added to the entry as well.
This would help identifying missing translations for when the translation of a publication is added.