Fix a few bugs introduced in file upload rework

* Fix the widget picture_snapshot command (not that I can find
   anything that uses it)
 * Remove unused prop
 * Fix plural on ContentMessages

src/components/structures/RoomView.js

@@ -536,7 +536,9 @@ module.exports = React.createClass({
                   payload.data.description || payload.data.name);
               break;
             case 'picture_snapshot':
-                this.uploadFile(payload.file);
+                return ContentMessages.sharedInstance().sendContentListToRoom(
+                    [payload.file], this.state.room.roomId, MatrixClientPeg.get(),
+                );
                 break;
             case 'notifier_enabled':
             case 'upload_started':