Using the `_html` suffix in an i18n key is the same as using `html_safe`
on it, which means that translation could potentially be used for XSS
attacks.
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.
When we grouped the fields together, the last one turned into a
`last-child`, which foundation automatically aligns to the right.
The markdown editor also needed to be tweaked a little bit.
This way we can show/hide that div when displaying translations, and we
can remove the duplication applying the same logic to the label, the
input, the error and the CKEditor.
This way we also solve the problem of the textarea of the CKEditor
taking space when we switch locales, as well as CKEditor itself taking
space even when not displayed.
Updating it required reorganizing the form so translatable fields are
together.
We also needed to add a `hint` option to the form label and input
methods so the hint wouldn't show up for every language.
Finally, the markdown editor needed to use the same globalize attributes
as inputs, labels and hints, which adds a bit of duplication.
