Update TinyMCE editor to v4.7.6 release

Fixes issue with double scroll bar and subsequent position of inline editing toolbar.

gui/public/tinymce/plugins/hr/plugin.js

@@ -1,39 +0,0 @@
-(function () {
-var hr = (function () {
-  'use strict';
-
-  var PluginManager = tinymce.util.Tools.resolve('tinymce.PluginManager');
-
-  var register = function (editor) {
-    editor.addCommand('InsertHorizontalRule', function () {
-      editor.execCommand('mceInsertContent', false, '<hr />');
-    });
-  };
-  var $_6bjkyabjjcun3xxm = { register: register };
-
-  var register$1 = function (editor) {
-    editor.addButton('hr', {
-      icon: 'hr',
-      tooltip: 'Horizontal line',
-      cmd: 'InsertHorizontalRule'
-    });
-    editor.addMenuItem('hr', {
-      icon: 'hr',
-      text: 'Horizontal line',
-      cmd: 'InsertHorizontalRule',
-      context: 'insert'
-    });
-  };
-  var $_1k15zabkjcun3xxn = { register: register$1 };
-
-  PluginManager.add('hr', function (editor) {
-    $_6bjkyabjjcun3xxm.register(editor);
-    $_1k15zabkjcun3xxn.register(editor);
-  });
-  var Plugin = function () {
-  };
-
-  return Plugin;
-
-}());
-})()