[Delivers #83811162] Allow disabling sharing dialog in playlab freeplay

This adds the "disable sharing" level builder option to Play Lab levels (it was previously only available in Artist levels).

This also updates the feedback dialog in this mode (freeplay with sharing disabled) to display the proper string when passing a level rather than always displaying "Congratulations! You have solved the final puzzle."

This is how the dialog now appears when this option is selected:
![image](https://cloud.githubusercontent.com/assets/56541/5275173/a9e5ca82-7a54-11e4-9d72-6267a0b32dfc.png)

Do we never have message = msg.finalStage now?