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/deferred-leveldown/deferred-iterator.js

@@ -0,0 +1,37 @@
+var AbstractIterator = require('abstract-leveldown').AbstractIterator
+var inherits = require('inherits')
+
+function DeferredIterator (db, options) {
+  AbstractIterator.call(this, db)
+
+  this._options = options
+  this._iterator = null
+  this._operations = []
+}
+
+inherits(DeferredIterator, AbstractIterator)
+
+DeferredIterator.prototype.setDb = function (db) {
+  var it = this._iterator = db.iterator(this._options)
+  this._operations.forEach(function (op) {
+    it[op.method].apply(it, op.args)
+  })
+}
+
+DeferredIterator.prototype._operation = function (method, args) {
+  if (this._iterator) return this._iterator[method].apply(this._iterator, args)
+  this._operations.push({ method: method, args: args })
+}
+
+'next end'.split(' ').forEach(function (m) {
+  DeferredIterator.prototype['_' + m] = function () {
+    this._operation(m, arguments)
+  }
+})
+
+// Must defer seek() rather than _seek() because it requires db._serializeKey to be available
+DeferredIterator.prototype.seek = function () {
+  this._operation('seek', arguments)
+}
+
+module.exports = DeferredIterator