Filtering/vtkGraph.cxx:
  - Fix addition of vertices and edges with properties

Parallel/vtkPBGLRMATGraphSource.cxx:
  - Make sure we handle all log2 bits!
  - Fix generation of edge IDs to make them contiguous

Parallel/vtkPBGLCollectGraph.cxx,
Parallel/vtkPBGLCollectGraph.h,
Parallel/Testing/Cxx/TestPBGLCollectGraph.cxx:
  - New filter, which collects a distributed graph into a non-distributed graph