Replaces use of fetchPatients() by patient mapping in QueryResult.
Replaces Lists with Sets, removes Study from signature.
Moves getting of patients to QueriesResourceService.
Updates retrieveData signature.

Includes Sets, excludes Study.
Adds override.
Remove redundant conditions on availability of patientIds and concept codes.
Merge branch 'master' into features/cherkasy-implement-observations-calls2
Add test for new retrieveData method.
Merge pull request #28 from thehyve/features/cherkasy-implement-observations-calls2

Features/cherkasy implement observations calls2