next iteration

- changed structure - all gui manipulations are done in main thread with
wx events;
- added date-time to messages;
- added tray notification;
- added main window minimizing to tray and getting back on double click;
- added writing to files all dialogs and reading from file on tab
opening;
- added disconnect handler;
- added sound for incoming message along with tray notification;
- improved tray icon behaviour;
- main window is opened on tray notification click;
- added font and font colour preferences;