This class represents a Group of Users in the system that are associated
with specific entity or resource. The users belonging to the Group may have
various Roles. The Permissions to perform actions upon the resource depend
on the Roles in the Group that they are assigned.
author: Rafal Krzewski author: Henning P. Schmiedehausen author: Marco Knüttel version: $Id: SecurityEntity.java 534527 2007-05-02 16:10:59Z tv $