Escape html in help_text
Escape html in help_text

The text won't be re-escaped in templates, so that both
admin and public forms render nice.

vcorreze/agendaEteAccoord,mlhamel/agendadulibre,mlhamel/agendadulibre,vcorreze/agendaEteAccoord,mlhamel/agendadulibre,vcorreze/agendaEteAccoord