Merge pull request #6210 from jfsiebel/configurable-shortcut-list

...orts/api/users-settings/server/methods/addUserSettings.js

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

.../imports/ui/components/audio/audio-controls/component.jsx

bigbluebutton-html5/imports/ui/components/chat/component.jsx

...ebutton-html5/imports/ui/components/nav-bar/component.jsx

...rts/ui/components/nav-bar/settings-dropdown/component.jsx

...n-html5/imports/ui/components/shortcut-help/component.jsx

...ton-html5/imports/ui/components/shortcut-help/service.jsx

...orts/ui/components/user-list/chat-list-item/component.jsx