Changed "checkXXXExist(...)" checks

Changed the signatures of methods of the form "checkXXXExists" so that
they took an identifier field rather than a whole business class object.
This was done to help simplify the code of methods in the retrieval
services, where we only cared about the identifier for a given type of
object rather than having a full instance of one with all its other
fields.
Adding display name method

StudyResultRetrievalContext is really meant to be a simple data
container class to hold a set of identifier values that commonly appear
in the web service calls related to retrieving results.  When errors
occur it is often useful to have a display name for a parameter that was
involved in a call.  In this case, getDisplayName() does not produce a
name that is as easily readable as those of other business classes that
specifically relate to epidemiologist concepts (eg: health code, study,
covariate, etc.).  However, this class has been developed more to aid
the middleware more than provide a meaningful concept to people.  The
retrieval context object may need to be moved in future to another
package, given that a context here isn't really a business concept.
Major refactoring of code for services

Previously, all the methods used by both the study submission and study
retrieval class were defined in RIFJobSubmissionAPI and implemented by
the ProductionRIFJobSubmissionService class.  This lead to the bloat
occurring in both of these files.  Therefore, code for the services was
redistributed into two services: a RIFStudySubmission service and a
RIFStudyResultRetrieval service.   Methods common to the two services
were isolated into an abstract superclass. The classes used to wrap
results from the main Java APIs were themselves refactored in a fashion
similar to the way the code for the main services was done.  Much of the
code in the classes used to support result retrieval are heavily stubbed
and will be implemented through more focused changes later.