[FEAT] Put Ensemble Numbers in the input file name

[aaronjridley]

Is your feature request related to a problem? Please describe.

If the user wants to control inputs with the ensembles, then the user can create input files and then have the code read those files based on the ensemble number.

Describe the solution you'd like
In the aether.json file, the user could enter the input file names as something like imf_%%%.dat and Aether would recognize %%% as needing to substitute 000, 001, 002, etc. for the ensemble number.

Describe alternatives you've considered
This should be straightforward.

Additional context
The user can already perturb the inputs, so this isn't super critical, but gives the user a lot more control.