Sometimes we're interpolating a link inside a translation, and marking
the whole translations as HTML safe.
However, some translations added by admins to the database or through
crowdin are not entirely under our control.
Although AFAIK crowdin checks for potential cross-site scripting
attacks, it's a good practice to sanitize parts of a string potentially
out of our control before marking the string as HTML safe.
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.
