Nothing said that the EmailRegistration plugin was meant to restrict
the nickname to the local part of the email address. Let users change
it before they actually register the user.
lib/plugin.php now has a parent onAutoload function that finds most common
files that are used in plugins (actions, dataobjects, forms, libs etc.) if
they are put in the standardised directories ('actions', 'classes', 'forms',
'lib' and perhaps some others in the future).
