[#575] Bulk update monitoring fields on surveyedLocales

* This method updates the 'displayName', which consists of answers given to questions in the registration form, the 'surveyGroupId', which is the id of the survey group, and the 'surveyInstanceContrib'
[#576] Bulk create new identifiers for surveyedLocales

* The method is idempotent against existing identifiers of the shape xxx-xxx-xxx.
* Older identifiers of the shape yyyyyyyy are reused as yyyy-yyyy-xxxx
[#581] Add dashes to identifiers created in server
Merge branch 'develop' into feature/575-576
[#575] Use background queue and processor
[#575] Return empty list instead of null
[#576] Use background queue and processor
[#575] Check for LastSurveyalInstanceId null

* also use WARNING as log level
[#576] Some old ids have 9 chars
Merge pull request #582 from akvo/feature/575-576

Features 575, 567, 581