OO-753: remove the optimistic locking from SecurityGroupMemebership and make almost all field immutable

OO-749: check if the controller is disposed before updating the business path (with back is possible)

OO-747: in case of a login with no sites, no tabs, place a dummy panel and a gui stack to prevent the red screen

OO-737: hardened the method to prevent an exception in the renderBodyOnLoad (which is probably not usefull)

OO-531: workaround to fix the freeze of the form in IE8 (but don't break in other browsers) if a rich text editor is used

OO-735: fix the query used by the portlets "my courses" and "my supervised courses", fix the setup script for MySQL 5.6.10 and greater

OO-705: switch the format of pdf's thumbnails to png, implements small admin panel to reset the thumbnails

OO-702: remove the fallback if there isn't any mailing definition, check first the default settings and send e-mails only if it's mandatory