use a foldable widget for all add layer actions

![fold1](https://f.cloud.github.com/assets/127259/736344/abf8b420-e314-11e2-96d5-3d638a55c5a8.png)
![fold0](https://f.cloud.github.com/assets/127259/736345/abfee62e-e314-11e2-9a99-4b9efa664842.png)