Make material, geometry and loadcase files easily

[mehady007]

mat_geom_load.ipynb
Reference: DAMASK_examples
Generate DAMASK material and geometry files for (currently) a single-phase material.

This class provides:
1) Material generation:
- By supplying YAML files describing the phase, elastic law, and plastic law,
you can create a DAMASK material file for N grains with random orientations.
2) Geometry generation (Voronoi tessellation):
- You can generate geometries either by specifying:
a) grid-per-grain (resolution defined relative to number of grains), or
b) explicit pixel/cell resolution (exact cell counts in x, y, z).
Notes on key options
--------------------
same_material : bool
If True, uses the same seeds across multiple generated geometries so that the
microstructure (grain size distribution and topology) and orientations can be
kept consistent while changing the resolution.
If False, seeds are regenerated for each geometry (different microstructures).
comp_strain : float
Used only in gen_geom_by_grid_per_grain. It allows starting with non-unity
voxel aspect ratio by modifying grid density in the z-direction.
Practically:
- z cell count is scaled by 1/(1 - comp_strain)
- x and y are then rescaled to keep total number of cells approximately conserved
This changes grid density along z while keeping volume/size the same.

Generate a 2-step plane strain compression loadcase (lab X):