Version 1.2.8 : Adds direct front-end slave sites creation

In this JMS multisites for joomla! version, you can now directly add a slave site from the front-end without a first access to the list of slave site.

We also added the possibility to use a "redirect URL" when the process is completed to avoid display the list of slave site or return to another page.

When working with "billable websites", we also have removed a PHP warning displayed when the status of website is modified.