[FIX] web: deal with reference fields

The reference fields haven't been correctly implemented with the new views.
This commit restores their behaviour.

Note that an small improvement has been introduced in this commit.
Before saas-16, a `name_get` was done for each record (so 80 if the field
was displayed in a full list view), which is not optimal. The calls are now
batched by model (so one `name_get` by model appearing in the field values).