[TxMt] Turn off "Save on unfocus application" for unsaved documents

[Andreas Wahlin]

> I think this might be a useful preference/fix.. lots of times I  
> open scratch documents in TxMt to copy and pasted into my web  
> browser. Constantly switching back and forth between them, I end up  
> having to cancel the "save as" dialog every time I return to the app.

I'd rather it was just turned off for the "Untitled" documents, or  
possibly even documents outside a project scope.

Andreas