fix a11y stuff in individual rooms-groups, closes #1094

lib/classes/sidebar/RoomClipboardWidget.class.php

resources/assets/javascripts/bootstrap/clipboard.js

resources/assets/javascripts/bootstrap/resources.js

resources/assets/javascripts/lib/actionmenu.js

resources/assets/javascripts/lib/clipboard.js

resources/assets/stylesheets/less/clipboard.less

resources/assets/stylesheets/scss/resources.scss

templates/sidebar/clipboard-area.php

templates/sidebar/clipboard-widget.php

templates/sidebar/room-clipboard-item.php

templates/sidebar/room-clipboard-widget.php