Option to minimize instead of exit

[naevtamarkus]

Dear developers,

I'd like to kindly ask for a checkbox in the settings page that we can enable to prevent davmail from exitting when we close the main window; being davmail a service (unlike e.g. a calculator) that needs to be active all the time, having accidentally close the window is, at least in my case, a frequent source of pain. Specially in ubuntu, where we lack of proper tray icon support.

Thanks a lot to all of you for this amazing (and sadly one of the last) tool that allows us linux users to use our favorite OS in a typical office/M$ work setting.

[mguessan]

This would probably make sense... however I don't think we have an exit menu at the moment, so just avoiding the exit on window close would not be enough