DEM8_Benchmarks

Hi,

Here I push the Silo Flow and the Penetration Test scripts using SI units (m-N-Pa-kg).

The organizers provided the initial sphere packings for all tests and modified the descriptions of the benchmarks. I slightly reorganized the provided data to work with the format of ymport.text for all three tests.

The provided .stl files were not in the same units or coordinate system as the initial packing, and so I imported the boundaries from provided .txt files of all facets (which were), writing the function ymport.textFacets. If we don't want this function in the ymport module forever, I can move it inside the scripts of these benchmarks, just let me know.

Vasileios

PS: in time we can remove the .stl files from this MR altogether; I mainly added them for us to have a full picture of the input data at this stage.