Metadata file is not saved

[farhantasy]

The metadata file is not saved when the output trace density field datacube is saved. This makes it difficult to identify the input parameters of a specific fit.

Here is an example what the metadata file looked like with PolyPhorm:

_dataset: data/TNG/TNG100_galmcpm_99_t=0.0
number of data points: 49903
number of agents: 5M
simulation grid resolution: 512 x 512 x 512 [vox]
simulation grid size: 110.715 x 110.715 x 110.715 [mpc]
simulation grid center: (55.3593, 55.3605, 55.3577) [mpc]

move distance: 0.1 [mpc]
move distance grid: 0.462448 [vox]
sense distance: 2.35 [mpc]
sense distance grid: 10.8675 [vox]
move spread: 10 [deg]
sense spread: 20 [deg]
persistence coefficient: 0.91
agent deposit: 0
sampling sharpness: 2.51192_