cordova-plugin-dialogs support more confirm choices on Windows

In cordova-plugin-dialogs the confirm dialog has a quirk where it cannot display more than 2 buttons on Windows mobile or more than 3 buttons on Windows desktop. This can be solved by using `Windows.UI.Popups.PopupMenu` instead of `Windows.UI.Popups.MessageDialog` as documented in <https://docs.microsoft.com/en-us/uwp/api/windows.ui.popups.popupmenu>.

An alternative idea to support yes-no-cancel choices on Windows desktop and mobile is described in: https://maximelabelle.wordpress.com/2016/03/02/displaying-a-yes-no-cancel-message-dialog-in-a-universal-windows-platform-uwp-app/