Make the meta description tag have a good static default value

static/js/app.js

@@ -4203,6 +4203,11 @@ quayApp.run(['$location', '$rootScope', 'Restangular', 'UserService', 'PlanServi
       $rootScope.description = 'Hosted private docker repositories. Includes full user management and history. Free for public repositories.';
     }
 
+    // Note: We set the content of the description tag manually here rather than using Angular binding
+    // because we need the <meta> tag to have a default description that is not of the form "{{ description }}",
+    // we read by tools that do not properly invoke the Angular code.
+    $('#descriptionTag').attr('content', $rootScope.description);
+
     $rootScope.fixFooter = !!current.$$route.fixFooter;
     $rootScope.current = current.$$route;
   });