[io][vtkreader][test] Add vtk reader tests with alu in sequential and parallel

test/io/gridmanager/CMakeLists.txt

test/io/gridmanager/gridmanagertests.hh

test/io/gridmanager/grids/disk.vtu

test/io/gridmanager/test_gridmanager_dgf.cc

test/io/gridmanager/test_gridmanager_vtk.cc

test/io/gridmanager/test_gridmanager_vtk.input

...eferences/test_gridmanager-disk-tri-element-reference.vtu

...s/test_gridmanager-disk-tri-element-refined-reference.vtu

...references/test_gridmanager-disk-tri-vertex-reference.vtu