Add DTMF handling for '*' (repeat menu) and '#' (return to menu/exit)

Adds support for the following DTMF buttons:

'*' - repeats the last menu.
'#' - exits from the change folders prompt. If already in the main menu, plays bye and hangs up.
This is mostly repeated from code used previously to list folder options. This should be moved to a method attached to the finite state machine like getMenu and used by both code paths.