admin(major): add YAMLField for attributes, add codemirror editor

passbook/admin/static/codemirror/mode/d/test.js

@@ -0,0 +1,11 @@
+// CodeMirror, copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: https://codemirror.net/LICENSE
+
+(function() {
+  var mode = CodeMirror.getMode({indentUnit: 2}, "d");
+  function MT(name) { test.mode(name, mode, Array.prototype.slice.call(arguments, 1)); }
+
+  MT("nested_comments",
+     "[comment /+]","[comment comment]","[comment +/]","[variable void] [variable main](){}");
+
+})();