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

package.json

@@ -117,6 +117,7 @@
     "@babel/register": "^7.7.4",
     "@peculiar/webcrypto": "^1.0.22",
     "@types/classnames": "^2.2.10",
+    "@types/flux": "^3.1.9",
     "@types/modernizr": "^3.5.3",
     "@types/qrcode": "^1.3.4",
     "@types/react": "16.9",