add confirmation when the moderator choose to close the session after quit

...uebutton-client/branding/default/style/css/BBBDefault.css

bigbluebutton-client/locale/en_US/bbbResources.properties

bigbluebutton-client/locale/pt_BR/bbbResources.properties

...tton-client/src/org/bigbluebutton/main/events/BBBEvent.as

...client/src/org/bigbluebutton/main/views/LogoutWindow.mxml

...-client/src/org/bigbluebutton/main/views/MainToolbar.mxml