This event is fired if wodAppUpdate detected
"leftover" files from previous run - and they are
sufficient to replace and update your application without
performing new check and new download.
From within this event you can all Update
method to immediately update your application, or you can
call Clear method
to delete those files and start over.
You can also use PrevExist
property for this purpose, even before this event fires, if
you want to check if "leftover" exist immediately
after initializing wodAppUpdate.