various improvements while preparing for resolution of #761

Device/Data/DataUtil.cpp

@@ -65,7 +65,7 @@ DataUtil::transpose(const std::vector<std::vector<double>>& original)
 Datafield DataUtil::createRearrangedDataSet(const Datafield& data, int n)
 {
     ASSERT(data.rank() == 2);
-    n = (4 + n % 4) % 4;
+    n = (n % 4 + 4) & 3; // modulo 4, also for negative arguments
     if (n == 0)
         return data;