Prevent RoomTiles from being dragged into other droppables

for the time being at least.

src/components/structures/RoomSubList.js

@@ -572,7 +572,11 @@ var RoomSubList = React.createClass({
                 { subList }
             </div>;
 
-            return this.props.editable ? <Droppable droppableId={"room-sub-list-droppable_" + this.props.tagName}>
+            return this.props.editable ?
+                <Droppable
+                    droppableId={"room-sub-list-droppable_" + this.props.tagName}
+                    type="draggable-RoomTile"
+                >
                     { (provided, snapshot) => (
                         <div ref={provided.innerRef}>
                             { subListContent }

src/components/views/rooms/DNDRoomTile.js

@@ -41,6 +41,7 @@ export default class DNDRoomTile extends React.Component {
                 key={props.room.roomId}
                 draggableId={props.tagName + '_' + props.room.roomId}
                 index={props.index}
+                type="draggable-RoomTile"
             >
                 { (provided, snapshot) => {
                     return (