Switched on session handling
Created AccountServer class.
Add user name validation
Created stubs in AccountServer class.
Change handling of request for user authentication
Bagfix for reloading of page for idle plocess
The first version own challenge
The second version own challenge. Implemented separate authentication
process for each session.
removed unnecessary code
Created base classes for Message System
Created specific messages
Created WrongAbonentClassException and implemented MsgGetUserId class.
implemented the homework #3 assigned by instructor
Implemented the possibility of re-sign of a user after a bad entering of
the registration data. Fixed bug with incorrect display of the user ID.