demote html5 moderator user to viewer based on flag

...utton-html5/imports/api/users/server/modifiers/addUser.js

...ml5/imports/api/users/server/modifiers/createDummyUser.js

.../ui/components/actions-bar/actions-dropdown/component.jsx

...button-html5/imports/ui/components/settings/component.jsx

bigbluebutton-html5/private/config/public/app.yaml

bigbluebutton-html5/private/config/public/user.yaml