[#435] Copy question group

Change the *copy question group* functionality to enable copying all questions contained within the group.  Copying of the questions is now fired off as a task. 

Pending issues to address are: 
* How to notify the user that questions are still being copied and they need to wait for completion
* How to refresh question group after copying is completed
It is for later. Its not related to these changes but rather marked for a code cleanup.