Minimize to tray

On Linux there is a bug that tray icon does not show always due to XEmbed issue.
On Windows 8.1 works fine.
More: 
http://www.qtcentre.org/threads/56459-QSystemTrayIcon-and-linux
https://bugreports.qt-project.org/browse/QTBUG-34364


Small modification to set up behaviour on close window button.
![516e7e97-4700-42fa-8a32-de4a3ebcc4b4](https://f.cloud.github.com/assets/3951334/2416029/4ef91e84-aafd-11e3-9709-6bb356cfd7a0.png)
Tray support ContextMenu where user can set his status. Right now Tray Icon shows only static icon.
Icon should reflect status that user has. Maybe add small rectangle in the corner of logo to reflect status(green for Online, red for Busy etc).
![e038aa23-3550-4a21-901b-c02690a9d7f7](https://f.cloud.github.com/assets/3951334/2416030/4f5cea90-aafd-11e3-8e30-3ec64d42bbdd.png)

Sorry for close/reopen, missclicked ;)