Initial breakout for room list rewrite

This does a number of things (sorry):
* Estimates the type changes needed to the dispatcher (later to be replaced by https://github.com/matrix-org/matrix-react-sdk/pull/4593)
* Sets up the stack for a whole new room list store, and later components for usage.
* Create a proxy class to ensure the app still functions as expected when the various stores are enabled/disabled
* Demonstrates a possible structure for algorithms

src/stores/room-list/models.ts

@@ -0,0 +1,36 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export enum DefaultTagID {
+    Invite = "im.vector.fake.invite",
+    Untagged = "im.vector.fake.recent", // legacy: used to just be 'recent rooms' but now it's all untagged rooms
+    Archived = "im.vector.fake.archived",
+    LowPriority = "m.lowpriority",
+    Favourite = "m.favourite",
+    DM = "im.vector.fake.direct",
+    ServerNotice = "m.server_notice",
+}
+export const OrderedDefaultTagIDs = [
+    DefaultTagID.Invite,
+    DefaultTagID.Favourite,
+    DefaultTagID.DM,
+    DefaultTagID.Untagged,
+    DefaultTagID.LowPriority,
+    DefaultTagID.ServerNotice,
+    DefaultTagID.Archived,
+];
+
+export type TagID = string | DefaultTagID;