Rename output files

[damianooldoni]

This PR:

1. improves names of output files, following style in trias-project/occ-alien.
2. Change extension output files, from tsv to csv ( see Save all outputs as csv instead of tsv #3).
3. Modify all references to tsv in textual parts of the pipeline (see Save all outputs as csv instead of tsv #3).

These output files are not pushed to remote as they could be very big (e.g. Belgian occurrence cube is ~ 524MB), so they are not visible in "./data/processed". As processed subdirectory remains empty, it is also not present on remote.