Fixed example.
Simplified design of tag components.
Added util for root exception cause retrieval.
Improved exception handling in HTTP request processing.
Added utils for role-based security checks.
Added "access denied" security util in HTTP exchange for convenience.
Included user roles information in basic user info storage.
Implemented role-based security checks for for app screens.
Configured role-based security for the "admin" screen.
Added support for role-based per-class access authorization in HTTP module.
Improved role-based screen authorization (covered event handling).
Fixed role-based security check bug.