Custom MessageBox with logging capabilities and offscreen/scripting support

I propose a custom MessageBox. The differences to QMessageBox:

• every info/warning/error is also logged at the appropiate level (after #82 (closed) this should be reflected properly)
• if one is running PeTrack with e.g. autotrack, only logging is enabled to ensure that scripts run without human supervision

We would still implement an API like QMessageBox::info() to enable easy replacement and easy use.

To Discuss:

Do we need to differentiate between these logs and the usual stuff? Do people usally read the log of PeTrack after running autotrack?

• PMessageBox class with static function for building a dialog
• Logging and wrapper macro
• Graphical feedback only if not run with -platform offscreen