cleanup include files and add constructors for datacollector and gridcreators

dune/vtk/datacollectorinterface.impl.hh

dune/vtk/datacollectors/continuousdatacollector.hh

dune/vtk/datacollectors/discontinuousdatacollector.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/forward.hh

dune/vtk/gridcreatorinterface.hh

dune/vtk/pvdwriter.hh

dune/vtk/pvdwriter.impl.hh

dune/vtk/vtkreader.hh

dune/vtk/vtkreader.impl.hh

dune/vtk/vtktimeserieswriter.hh

dune/vtk/vtktimeserieswriter.impl.hh

dune/vtk/vtktypes.cc

dune/vtk/vtkwriterinterface.hh

dune/vtk/vtkwriterinterface.impl.hh