FRE-600: Fix code review blockers

- Consolidated duplicate UndoManagers to single instance
- Fixed connection promise to only resolve on 'connected' status
- Fixed WebSocketProvider import (WebsocketProvider)
- Added proper doc.destroy() cleanup
- Renamed isPresenceInitialized property to avoid conflict

Co-Authored-By: Paperclip <noreply@paperclip.ing>

node_modules/serialize-error/readme.md

@@ -0,0 +1,31 @@
+# serialize-error [![Build Status](https://travis-ci.org/sindresorhus/serialize-error.svg?branch=master)](https://travis-ci.org/sindresorhus/serialize-error)
+
+> Serialize an error into a plain object
+
+Useful if you for example need to `JSON.stringify()` or `process.send()` the error.
+
+
+## Install
+
+```
+$ npm install --save serialize-error
+```
+
+
+## Usage
+
+```js
+const serializeError = require('serialize-error');
+const error = new Error('unicorn');
+
+console.log(error);
+//=> [Error: unicorn]
+
+console.log(serializeError(error));
+//=> {name: 'Error', message: 'unicorn', stack: 'Error: unicorn\n    at Object.<anonymous> ...'}
+```
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)