* Add custom message for inclusion validation to include the allowed values.
* Force user to choose document_type from select lik the one shown at verification form.
* Convert stored document_type to a human readable text
This way we can simplify the way we generate form fields. In some cases,
we also use the human attribute in table headers, which IMHO makes
sense.
I haven't moved all of them: for example, sometimes a label is
different depending on whether it's shown to administrators, valuators,
or users. And I haven't touched the ones related to devise, since I
wasn't sure about possible side effects.
Note I've also removed placeholders when they had the same text as their
labels, since they weren't helpful. On the contrary, the added redundant
text to the form, potentially distracting users.
* Create admin controller and routes
* Add pagination
* Add search by document_number
* Add EN and ES translations
* Add index specs
* Add missing model specs
