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/stackback/test.js

@@ -0,0 +1,24 @@
+var assert = require('assert');
+var stackback = require('./');
+
+test('capture', function() {
+    var err = new Error();
+    var stack = stackback(err);
+    assert.equal(stack[0].getFileName(), __filename);
+});
+
+// calling stackback on the same error twice should work
+test('multiple calls', function() {
+    var err = new Error();
+    var stack1 = stackback(err);
+    var stack2 = stackback(err);
+    assert.equal(stack1[0].getFileName(), __filename);
+    assert.deepEqual(stack1, stack2);
+});
+
+test('string', function() {
+    var err = new Error();
+    stackback(err);
+    assert.equal(typeof err.stack, 'string');
+});
+