Major changes:
* New VTK/ folder to enable OSUFlow to load various file formats and handle different data types (e.g., curvilinear, unstructured datasets)
  Enable WITH_VTK flag in CMake to compile codes in VTK/ .  Run examples in VTK/examples. vtk<->vec file format conversion is also provided.
  See detail in https://github.com/chunmingchen/OSUFlow/wiki
* Fix of the memory allocation commands in assertion statements in ParFlow.C
* New verification codes in tests/ to verify the computation outputs is the same as those by the stable vesion.
  To run the tests, turn on WITH_TESTING in CMake and run the script tests/VERIFY_OUTPUT

More changes:
* CMakeLists.txt fixes, including GL/GLU/GLUT library uses, linking order and compatility with or without MPI, GRAPHICS.
* More sample datasets in sample_data/

Note:
* WITH_PARAVIEW flag and the related Paraview plugins in VTK/plugins are not fully tested in this revision yet.

Description for each file/folder:

VTK/* :
  VTK integration
src/Blocks.C :
  make compilable when MPI is not used
src/Field.h :
  Make all functions virtual for VTK integration
src/Grid.h :
  add more CellType enums for VTK integration
src/OSUFlow.h :
  add public function hasData() for checking whether data are ready for VTK integration
src/ParFlow.C, src/ParFlow.h :
  assertion fix.  Allows users to assign MPIComm.
Regular/Parallel/SimpleMpiDraw.C :
  Backup of MpiDraw without VTK.
Regular/Serial/FileDraw.C :
  Fix to be compilable without MPI
Regular/Serial/StreamlineSimple.C :
  Print results for output verification
sample_data/ :
  Add several datasets for VTK examples
tests/TestMPI/* :
  for verifying MPI computation output from VERIFY_OUTPUT script
tests/VERIFY_OUTPUT
  compares the outputs with the stable version.
tests/data/* :
  outputs from the stable version for verification

git-svn-id: https://svn.mcs.anl.gov/repos/osuflow/trunk@318 6b533941-e25a-0410-8d37-8675ae1e3315