The `UnitTestVTKDataSetReader` test reads in .vtk files of multiple
formats. The origins of this test predate the use of git-lfs and a data
directory, so the test defined in the source code several strings
containing the contents of the files.
That is no longer necessary. This change removes those strings from the
file and creates actual files in the data directory. This is easier to
manage as well as more convenient if you want to use the same data in a
different test or just take a look at the data in a different program
(such as VisIt or ParaView).
Fixed error in one entry of number_of_triangles table for MarchineCells that results in missing triangles for wedge cell type as reported by issue #496.
It makes me irrationally nervous to check an empty file as the sentinel
data. Instead, add some text that can be compared agains. Also add some
explenation to the file to prevent naive developers from messing with
the file.
