[Client][Server] Add some GUI.
[Server][View] Add simple view.
[Server][View] Add start tabs.
[Server][View] JPanel -> JList.
[Server][Server] Add getters.
[Server][SessionPool] Add extending Observable.
[Server][SessionPool] Add some comments.
[Server][SessionPool] Add display of session.
[Server][UserList] Add extending observable
[Server][Controller] ConnectedUser -> connection, connectedUsers.
[Server][Server] Add field connected users, getConnectedUsers().
[Server][View] Add display of allUsers, registeredUsers.