Complete query assembly; add autocomplete menu.

Add:
    static/js/index.advanced-search-form.js, static/sass/index.sass,
    static/css/lib/jqueryui.custom.min.css
        -Add `jQuery UI` autocompletion menu to the advanced-search form's
        language input field, to replace `twitter typeahead` (which was
        incompatible with the new form's style rules).

    static/js/index.advanced-search-form.js
        -Add regex field specifier to query string.