Add unregister_from_hub() method and rename some proteced methods.
Implement disconnect() method.

Implement unregistering from the Hub. For this purpose the unregister_from_hub() method has been created that sends the appropriate class to the Hub. Some of the other protected methods have been renamed to be more explicit.

Added also #include <fcntl.h> to make compatible to Fedora.
Test client disconnetion.
Add information about new VO module.