Prevent TagTiles from being dragged into other droppables

for the time being at least.

src/components/structures/TagPanel.js

@@ -95,7 +95,10 @@ const TagPanel = React.createClass({
             />;
         });
         return <div className="mx_TagPanel">
-            <Droppable droppableId="tag-panel-droppable">
+            <Droppable
+                droppableId="tag-panel-droppable"
+                type="draggable-TagTile"
+            >
                 { (provided, snapshot) => (
                     <div
                         className="mx_TagPanel_tagTileContainer"

src/components/views/elements/DNDTagTile.js

@@ -25,6 +25,7 @@ export default function DNDTagTile(props) {
             key={props.tag}
             draggableId={props.tag}
             index={props.index}
+            type="draggable-TagTile"
         >
             { (provided, snapshot) => (
                 <div>