Add startAsHidden and showSpinner props to RoomSubList

startAsHidden: Previously we never started in the hidden state and all was well.
But with archived rooms you DO want to start hidden as you haven't fetched the
room list yet. Without this, you need to click twice (close/open) before the
archived room list will load.

showSpinner: If true, will show a spinner iff there are 0 elements being displayed.
Used when fetching the archived room list in RoomList.

src/components/structures/RoomSubList.js

@@ -64,6 +64,8 @@ var RoomSubList = React.createClass({
         bottommost: React.PropTypes.bool,
         selectedRoom: React.PropTypes.string.isRequired,
         activityMap: React.PropTypes.object.isRequired,
+        startAsHidden: React.PropTypes.bool,
+        showSpinner: React.PropTypes.bool, // true to show a spinner if 0 elements when expanded
 
         // TODO: Fix the name of this. This is too easily confused with the
         // "hidden" state which is the expanded (or not) view of the list of rooms.
@@ -76,7 +78,7 @@ var RoomSubList = React.createClass({
 
     getInitialState: function() {
         return {
-            hidden: false,
+            hidden: this.props.startAsHidden || false,
             sortedList: [],
         };
     },
@@ -307,9 +309,11 @@ var RoomSubList = React.createClass({
             );
         }
         else {
+            var Loader = sdk.getComponent("elements.Spinner");
             return (
                 <div className="mx_RoomSubList">
                     { this.props.alwaysShowHeader ? this._getHeaderJsx() : undefined }
+                    { (this.props.showSpinner && !this.state.hidden) ? <Loader /> : undefined }
                 </div>
             );
         }