Keep track of and expose the study UIDs for a query

This allows use by ctkDICOMQueryRetrieve widget where multiple
servers may be queried for a given set of filters.  By knowing
the what studies were found by a series, it's possible to go
back and get the data from the correct server when it is time
to retrieve.

Libs/DICOM/Core/ctkDICOMQuery.cpp

@@ -158,6 +158,11 @@ QMap<QString,QVariant> ctkDICOMQuery::filters()
   Q_D(ctkDICOMQuery);
   return d->Filters;
 }
+QStringList ctkDICOMQuery::studyInstanceUIDQueried()
+{
+  Q_D(ctkDICOMQuery);
+  return d->StudyInstanceUIDList;
+}
 
 
 //------------------------------------------------------------------------------

Libs/DICOM/Core/ctkDICOMQuery.h

@@ -59,7 +59,11 @@ public:
   void query(ctkDICOMDatabase& database);
 
   /// Add a StudyInstanceUID to be queried
-  void addStudyInstanceUID ( QString StudyInstanceUID );
+  void addStudyInstanceUID( QString StudyInstanceUID );
+
+  /// Access the list of study instance UIDs from the last query
+  QStringList studyInstanceUIDQueried();
+
 
   ///
   // Filters are keyword/value pairs as generated by