Fix: Correct labeling of bipartite graph nodes

* Before: Although we partition columns the output suggested that the
  row nodes were colored in bipartite graphs
* This was caused by mislabeling in DotWriter, swapping c_ and r_ label
  prefixes.
* The way the labels are currently written this commit also swaps the
  pseudo side flag used for adjacency graphs for correct output

src/SparseTransform/Convert/DotWriter.cs

@@ -37,7 +37,7 @@ namespace SparseTransform.Convert
         private StringBuilder processAdjacencyGraph(AdjacencyGraph inputGraph, StringBuilder output)
         {
             output.AppendLine("graph G {");
-            processNodes(inputGraph.GetNodes(), output, true);
+            processNodes(inputGraph.GetNodes(), output, false);
             processEdges(inputGraph.GetNodes(), output, false);
             output.AppendLine("}");
             return output;
@@ -57,7 +57,7 @@ namespace SparseTransform.Convert
             output.AppendLine("\tforcelabels=true;");
             processNodes(inputGraph.GetLeftNodes(), output, true);
             processNodes(inputGraph.GetRightNodes(), output, false);
-            processEdges(inputGraph.GetLeftNodes(), output, true);
+            processEdges(inputGraph.GetRightNodes(), output, true);
             output.AppendLine("}");
             return output;
         }
@@ -100,7 +100,7 @@ namespace SparseTransform.Convert
         {
             foreach (GraphNode v in nodes)
             {
-                output.AppendLine(NodeLabel(v, (left ? "c_" : "r_")));
+                output.AppendLine(NodeLabel(v, (left ? "r_" : "c_")));
             }
         }