cleanup some closing logic...
cleanup some closing logic
* Single prompt on quit event
* Disabled leaving the kernel running on window close, as it doesn't make as much sense
now that there are multiple kernel windows
* Tabs respect confirm-exit setting
* Removed some obsolete kwargs from MainWindow.__init__, that are no longer used
Closing logic is still a bit wonky, depending on the ordering of tabs closed (masters, slaves, etc.).
also fix some spelling errors, and remove errant semicolons
