Move getFriendlyRoomName to Room. Add recalculate() function to cache info.

lib/models/room-state.js

@@ -25,6 +25,14 @@ function RoomState(roomId) {
     this.paginationToken = null;
 }
 RoomState.prototype = {
+    /**
+     * Get all RoomMembers in this room.
+     * @return {Array<RoomMember>} A list of RoomMembers.
+     */
+    getMembers: function() {
+        return utils.values(this.members);
+    },
+
     /**
      * Get state events from the state of the room.
      * @param {string} eventType The event type of the state event.