Add string representation of BindingNotification.
Add string representation of BindingNotification.

For easier debugging.

jkoritzinsky/Avalonia,SuperJMN/Avalonia,jazzay/Perspex,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,OronDF343/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,Perspex/Perspex,wieslawsoltes/Perspex,SuperJMN/Avalonia,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,akrisiun/Perspex,wieslawsoltes/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,grokys/Perspex,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,Perspex/Perspex,susloparovdenis/Perspex,MrDaedra/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,grokys/Perspex,OronDF343/Avalonia,susloparovdenis/Perspex,jkoritzinsky/Avalonia,susloparovdenis/Avalonia,MrDaedra/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,susloparovdenis/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Perspex