Merge branch 'release/1.6.8'
Add release notes 1.6.8
Issue #446 - Set default values for new SurveyInstances

* Set 1 for `userID` and a generated UUID for `uuid` to avoid problems
  when exporting the data
Merge branch 'hotfix/446'
Add release notes for 1.6.8.1
Merge branch 'master' into develop