moved examples to tests

src/CMakeLists.txt

src/benchmark.cc

src/datacollector.cc

src/geometrygrid.cc

src/legacyvtkwriter.cc

src/pvdwriter.cc

src/structuredgridwriter.cc

src/test/CMakeLists.txt

src/timeserieswriter.cc

src/vectorwriter.cc

src/vtkwriter.cc