Add the possibility to use alias in the CLI

ex:

```
inputs:
  reference_elev:
    path_to_elev: "longyearbyen_ref_dem"
  to_be_aligned_elev:
    path_to_elev: "longyearbyen_ref_tba"
    path_to_mask: "longyearbyen_glacier_outlines"
  sampling_grid: null
```