Add readFile optional charset

Optional charset parameter required for correct file encoding detection
by browsers.
Add .interface classes to autoload index.
Add setError to mimic waJsonController::setError
Add waAuthAdapter::getFrontendUrl interface

Added waAuthAdapter::getFrontendUrl to allow override in children
classes.
Also added 'rel="nofollow"' to auth adapters links to disable search
engine robots.
Display VKontakte user screen name as user' site

If VKontakte user has screen_name set, display it as user site instead
of non-user-friendly 'idXXXX'