Fixes handle()-related strict warnings such as "Strict Standards:
Declaration of AdminPanelAction::handle() should be compatible with
Action::handle()"
Ref. #190
We're also now using $config['image']['jpegquality'] to determine the
quality setting for resized images.
To set Avatar max size, adjust $config['avatar']['maxsize']
The getAvatar call now throws exceptions too. Related changes applied.
Now let's move Profile->avatarUrl to the Avatar class!
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).
