OPAL-1688: DisclosurePanel for encoding options

![image](https://f.cloud.github.com/assets/2565497/233499/45ba977e-8756-11e2-82a4-f1bb3c88ee74.png)

![image](https://f.cloud.github.com/assets/2565497/233500/52c649d6-8756-11e2-902f-7be3cf84890a.png)