[#435] Create copy question group task
[#453] Refactor `SurveyUtils.copyQuestionGroup` to launch task

* `SurveyUtils.copyQuestionGroup` method launches task to copy questions and other elements in question group
* Added `sourceId` attribute to indicate question group being copied
* Remove unused `order` parameter in `SurveyUtils.copyQuestionGroup`
[#453] Source code formatting
Merge branch 'develop' into issue/435_copy_question_group
[#435] Append suffix to `questionId`
Merge pull request #784 from akvo/issue/435_copy_question_group

[#435] Copy question group