Fix search query special chars (#1605)

The search query used in the generateQueryString function does not
escape special characters specified in the escape_queries setting, and
the query provided to it by arElasticSearchPluginQuery has not been
previously escaped either. Updating this to call escapeTerm to escape
the search query so that this setting is respected.

plugins/arElasticSearchPlugin/lib/arElasticSearchPluginUtil.class.php

@@ -171,7 +171,7 @@ public static function getI18nFieldNames($fields, $cultures = null)
     /**
      * Generate a query string query.
      *
-     * @param string $query    escaped search term
+     * @param string $query    unescaped search term
      * @param array  $fields   fields to search (including culture if needed)
      * @param string $operator default query operator (AND/OR), default: AND
      *
@@ -180,7 +180,7 @@ public static function getI18nFieldNames($fields, $cultures = null)
     public static function generateQueryString(
         $query, $fields, $operator = 'AND'
     ) {
-        $queryString = new \Elastica\Query\QueryString($query);
+        $queryString = new \Elastica\Query\QueryString(self::escapeTerm($query));
         $queryString->setDefaultOperator($operator);
         $queryString->setFields(self::getBoostedSearchFields($fields));
         $queryString->setAnalyzer(