Give users control of admin and user menu options in conferences

Currently there is only a single control that allows an admin to control conference dtmf menus, allow or deny. The menu dtmf options are hard coded and permit controlling things like mute with a single key press. For systems with stray dtmf issues or talk-off, users can be muted accidentally.

Suggest that GUI options be added to allow individual enable/disable of admin and user menus, and allow users to set which dtmf sequences control which option.