Fixed build error on GCC 4.7

For soem reason, we have to link to R. We need to fix this but for time
being applying Hari's patch.
Merge remote-tracking branch 'github/r_integration' into r_integration

* github/r_integration:
  Fixed build error on GCC 4.7
Fixed build error on GCC 4.7

For soem reason, we have to link to R. We need to fix this but for time
being applying Hari's patch.
Added export script for python
Merge remote-tracking branch 'origin/r_integration' into r_integration

* origin/r_integration:
  Fixed build error on GCC 4.7
Build MPI dependant library only when VTK_USE_MPI is ON
VTKExtensions requires ZLIB
prevent python path crash on mac

Change prevents paraview from automatically adding uvcdat build
tree to python path.
Merge branch 'uvcdat-master' into uvcdat-next
wrappers were crashing on POPMatrices