Add support for adding Client Certificates to access-lists

Client certificate support is added as a new separate type of option for
access-lists.

This commit is the support code to enable access-lists to contain
Client Certificate references.

frontend/js/app/nginx/access/form/clientca.js

@@ -0,0 +1,7 @@
+const Mn       = require('backbone.marionette');
+const template = require('./clientca.ejs');
+
+module.exports = Mn.View.extend({
+    template:  template,
+    className: 'row'
+});