Option for tray icon to display user status + misc stuff

Setting added for tray icon to be displayed as user status. Default value is **off** (original tox icon as it is now). Useful when user wants to see his current status in tray. Especially handy when auto-away kicks in, we immediately can see if we are away or not without a risk of breaking away status.

Theme options put into form layout. Labels and setting controls are lined up and look much better.

Main window geometry is saved when window is resized (on resizeEvent()) and main window splitter is saved when it is moved (on splitterMoved()). This gets rid of problem when most of the time window geometry would not be saved because code path in closeEvent() is not triggered due to tray settings.