fixes #259

- no confirmation alert sheet in iOS any more if user decides to delete multiple items (programs, objects, sounds or looks) via EditMenu (Note: PocketCode for Android still asks the user to confirm deleting multiple items in the current PlayStore version)
- but as discussed with Lukas Radacher I haven't removed the confirmation alert sheet if the user wants to delete only one item via the swipe-to-left gesture (reason for this: the user could accidentally tap on the red "Delete"-button by mistake instead of tapping on the "More"-button)
- at the last meeting we decided to not replace the confirmation alert sheets by action sheets, because Apple also uses alert sheets for confirmation requests e.g. in the iOS Mail app