Removed null checks from the constructor and related tests. We can rely on the container to inject correctly.
Moved out the various reference link url composition functions into a separate component (UrlComposer).
Cleaned up StudyResource:
* Removed GET for individual StudySummary. GET /study/{studyId} now maps to StudyDetails.
* Moved dataset summary information up to the StudySummary level
* Removed methods that exposed whole workbook object for Nurseries and Trials.
Fixed the integration test that was failing due to incorrect assertions for the data in Rice study used.