update jingo: update Jinja2 from 2.7.1 to 2.7.2
update jingo: remove useless |safe and |xssafe filters on Markup object (localized strings with Tower)
update jingo: fix |safe usage

Rules:
* a localized string _(...) is always seen as safe as it's a Markup
  object (thanks to Tower), and doesn't need to be marked as safe
* a "loc" string isn't marked as safe, and as such, needs to be marked
  safe or it'll be escaped
* doing string interpolation (with |f) preserves the safeness or the
  original string, but escapes its input if they're not marked as safe:
  SAFE|f(foo) will return a safe string with foo escaped (if not marked safe),
  UNSAFE|f(foo) will return an unsafe string, but foo won't be escaped yet,
  the final result needs to be marked as |safe to be unescaped

Additional notes: links with no "&" don't need to be marked safe as
escaping them doesn't change anything, same thing for numbers, dates...