We were using similar code in four different places; six, if we count
the welcome pages seeds. Reducing duplication in the pages seeds is a
bit tricky because administrators are supposed to edit their content and
might remove the HTML class we use to define styles. However, we can
share the code everywhere else.
Note that there's a bug in the application since we show that level 2
users cannot vote for budget projects but we give them permission to do
so in the abilities model. We're keeping the same behavior after this
refactoring but we might change it in the future.
We had the same texts four times, with slight variations in the case of
the management section.
We're unifying them under the "verification" i18n namespace, since the
texts are about actions which can be done depending on whether users are
verified or not.
Note the names of the i18n keys aren't very consistent, since we use
"debates" in plural but "proposal" in singular. We're leaving it like
this so existing translations aren't affected.
