cleanup whitspaces and naming of writer classes

dune/vtk/CMakeLists.txt

dune/vtk/datacollectorinterface.hh

dune/vtk/datacollectorinterface.impl.hh

dune/vtk/datacollectors/CMakeLists.txt

dune/vtk/datacollectors/continuousdatacollector.hh

dune/vtk/datacollectors/discontinuousdatacollector.hh

dune/vtk/datacollectors/lagrangedatacollector.hh

dune/vtk/datacollectors/quadraticdatacollector.hh

dune/vtk/datacollectors/spdatacollector.hh

dune/vtk/datacollectors/structureddatacollector.hh

dune/vtk/datacollectors/unstructureddatacollector.hh

dune/vtk/datacollectors/yaspdatacollector.hh

dune/vtk/defaultvtkfunction.hh

dune/vtk/filereader.hh

dune/vtk/filewriter.hh

dune/vtk/forward.hh

dune/vtk/function.hh

dune/vtk/gridcreatorinterface.hh

dune/vtk/gridcreators/CMakeLists.txt

dune/vtk/gridcreators/continuousgridcreator.hh