add per user functionality to multi user whiteboard

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

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

...board-multi-user/server/methods/changeWhiteboardAccess.js

...ard-multi-user/server/modifiers/modifyWhiteboardAccess.js

...on-html5/imports/ui/components/presentation/component.jsx

...utton-html5/imports/ui/components/presentation/service.js

...ton-html5/imports/ui/components/user-avatar/component.jsx

...utton-html5/imports/ui/components/user-avatar/styles.scss

...st-content/user-participants/user-list-item/component.jsx

...st-content/user-participants/user-list-item/container.jsx

...r-participants/user-list-item/user-dropdown/component.jsx

...ui/components/whiteboard/whiteboard-toolbar/component.jsx

...ui/components/whiteboard/whiteboard-toolbar/container.jsx

...s/ui/components/whiteboard/whiteboard-toolbar/styles.scss

bigbluebutton-html5/private/locales/en.json