improve a11y in room-search, closes #1024

resources/assets/javascripts/bootstrap/resources.js

resources/assets/javascripts/lib/resources.js

resources/assets/stylesheets/scss/resources.scss

templates/sidebar/room-search-criteria-available-range.php

templates/sidebar/room-search-criteria-seats.php

templates/sidebar/room-search-criteria-templates.php

templates/sidebar/room-search-criteria.php

templates/sidebar/room-search-tree-widget.php

templates/sidebar/room-search-widget.php

templates/sidebar/time-range-filter.php