#64 MainWindow class refactoring

[Alex Chmykhalo]

• Get rid of useless includes in mainwindow.h (consider replacing with forward class declarations)
• Check name conventions for members and mehtods
• Get rid of unused includes in mainwindow.cpp file.
• Add GPL header to mainwindow.* files
• Move creation of tray menu to ApplicationBuilder
• Add Doxygen comments, get rid of commented and unused code