Simplelayout action pointing to shop item

Added a action to the shop item block:
![bildschirmfoto 2013-05-13 um 15 32 19](https://f.cloud.github.com/assets/7469/495794/bd4f40f0-bbd1-11e2-8356-b7b91fed9b60.png)

The action points to the shop item and is only visible for editors.

/cc @lukasgraf @maethu