Fixed Escaping Issue Affects Customization in Alf.io's Ticket Reservation System

Summary

alf.io is an open source ticket reservation system for conferences, trade shows, workshops, and meetups. Prior to version 2.0-M5, the preloaded data as json is not escaped correctly, the administrator / event admin could break their own install by inserting non correctly escaped text. The Content-Security-Policy directive blocks any potential script execution. The administrator or event administrator can override the texts for customization purpose. The texts are not properly escaped. Version 2.0-M5 fixes this issue.