Revert "Revert "CHERKASY-58 RESTful webservice. Implement /studies/<studyId>/concepts""

This reverts commit bca58c7e7f4115d18e776e2cd28c2ac0fdf0fec6.
Merge pull request #19 from thehyve/features/CHERKASY-implement-api-calls

Features/cherkasy implement api calls