Refactor translation import and update to improve custom types support.

review2431002
issue3566
Better cache usage in Menu.get_rec_name

By re-using the field function, it takes better advantage of the global cache.

issue3709
review3781002
Add unique filter on the cache ids in ModelStorage.__getattr__

_ids must be kept with duplicates because it is important to keep the right
order/proximity of records in the cache. But when reading the values, the ids
must be filtered to be unique to not read it twice.

issue3710
review3781003
Fix typo in Menu.get_rec_name introduced in changeset 127981430238