Utility Class - Implements an Exit Handler for DIM Servers
    There are 4 occasions where a DIM server would exit if no ExitHandler was declared:
        - The DIM_DNS_NODE is undefined
        - The DNS refuses connections from the machine where this server is
        - One of the services provided by this service is already declared by another server
        - The server got an "EXIT" command from a client.
        - The server got an "EXIT" command from the DNS
    If the user declares an exitHandler than it's is up to the user to decide whether to exit or not.

Public Functions :

• virtual void exitHandler ( int code ) ; To be overloaded by the user. Gets called when the server is requested to exit. The parameter code contains the error code that caused the exit request or the code sent by the client (if the request came from a client). Error codes are defined here.

    Example:

        class ExitHandler : public DimExitHandler
        {
            void exitHandler( int code )
            {   
                // cleanup
                cout << "Exiting... " << endl;
                exit(1);
            }
            public:
            ExitHandler() {DimServer::addExitHandler(this);}
        };