- with the xml append format it is possible to write raw binary
  (instead of base64), but the writer becomes more complicated.
  Either needs two passes to create, or need to allocate a block
  of space for the header information (like VTK itself does) and
  write later.

    * internalWriter
    * patchWriter
    * surfaceMeshWriter
    * lagrangianWriter

 Also these special purpose ones:
    * foamVtkWriteSurfFields