#111 Autosave after every new definition

If I think a few weeks back, I remember that FMSLogo crashes from time to time. And you know, FMSLogo is not the most stable program in the world, that happens just sometimes, for example at a recursion or similar. Especially because of this and because it's a development environment for children, FMSLogo should automatically save everything temporarily after every close of the editor, after every new definition. If FMSLogo crashes it should ask next time. whether the backup is to be loaded.