Added StudyConsentController

Not sure we need to set the current one to inactive when adding a new consent.  The method is generating too much  side-effect.  Imagine that the method sets the current to inactive and then fails to add the new one.  There would be no active consent.  That said, I prefer single-policy methods, methods that do one thing only.

We can have multiple active versions. Dynamo set up the version (the timestamp) as the range key.  The method retrieving the active consent always retrieves the newest version.