Add remember checkbox for remember guest policy choice

...luebutton-html5/imports/api/guest-users/server/methods.js

...ports/api/guest-users/server/methods/changeGuestPolicy.js

...n-html5/imports/ui/components/waiting-users/component.jsx

...n-html5/imports/ui/components/waiting-users/container.jsx

...tton-html5/imports/ui/components/waiting-users/service.js

...ton-html5/imports/ui/components/waiting-users/styles.scss

bigbluebutton-html5/private/locales/en.json