Port Cricket to use Toga, instead of Tkinter

Cricket's GUI interface is currently implemented using Tkinter, which has a lot of limitations. The main goal is the complete port of Cricket to use Toga as the framework for GUI interface. The base logic is mostly complete, so firstly I will plan how to adapt the actual architecture of the view to use Toga widgets. If I find one widget that Cricket uses but isn't implemented on Toga, I will develop a contribution to this specific widget. This way the application will not lose the basics layout. So, the proposal will not only focus on the port of Tkinter to Toga, but on mapping the necessary widgets for a real application using Toga framework. In addition of the advantages of using Toga instead of Tkinter as I highlighted, this is a opportunity to improve error handling and make better use of features that Toga has but Tkinter does not. It will be the first BeeWare project that “eats it is own dogwood".