PR it_start outputs + improvements module phys_fields2d + make black
Created originally on Bitbucket by calpe (Miguel Calpe)
Was already merged in Bitbucket before import, marked as merged by the import user
- Fix good it_start spatio_temporal_spectra and frequency_spectra.
- Improvements on module phys_fields2d.py
- Time interpolation class method plot.
- Make black calpe/fluidsim.