fix VTK out in demos
cherry pick VTK timed output by Jan Blechta and Johan Hake, i.e. unrevert reverted revs 7524, 7525
merge lp:~blechta/dolfin/vtk_out rev 7526: fix VTK out in demos
Merge work on timed VTL output for MeshFunctions and Mesh
Merge work on timed VTL output for MeshFunctions and Mesh:
   Jan Blechta 2013-03-14 [merge] merge lp:~blechta/dolfin/vtk_out rev 7526: fix VTK out in demos
   Jan Blechta 2013-03-13 fix VTK out in demos
   Jan Blechta 2013-03-14 cherry pick VTK timed output by Jan Blechta and Johan Hake, i.e. unrevert reverted revs 7524, 7525