[#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`
Merge pull request #763 from akvo/issue/760

[#760] Fixed
[#453] Source code formatting
Merge branch 'master' into develop
[#771] Ignore responses where `Question` object is not found
[#771] Source code formatting
Merge pull request #772 from akvo/issue/771_survey_responses_failing_deleted_question

[#771] Survey responses failing when a question is deleted from the survey
[#773] Release notes 1.7.3.1
Merge branch 'release/1.7.3.1'
Merge branch 'master' into develop
[#759] Add double entry flag in number questions
Merge pull request #776 from akvo/issue/759-doubleentry-numbers

[#759] Add double entry flag in number questions
[#775] Fixed
[#778] Fixed
[#768] Remove generated css files from version control and add the sass compilation step to the Dashboard build process
Merge pull request #777 from akvo/issue/775

[#775] Survey title shown as link that is not clickable
Merge pull request #779 from akvo/issue/778

[#778] Dialog box is cut in smaller screens. Screen not scrollable
[#299] Add survey title to XML

* Escape title string
[#768] Minify CSS files in production mode

* When used with RAKEP_MODE=production we want to "minify" the CSS file
  using YUI compressor
* We need to change the references to *.min.css