Dowml

- [3] Accept 'delete 2-5' to delete a range of jobs.
- [25] Replace 'inline' command (resp. attribute) in the Interactive
(resp. library) with 'inputs'. Deprecate 'inline'.
- [4] Introduce 'outputs' command to change the type of
outputs from inline to data-assets.
- [21] Read credentials from file $DOWML_CREDENTIALS_FILE
as last resort.

- Packaging-only changes

- [17] DOWMLLib now returns tabular outputs as dataframes by default.
Also replace the now-deprecated csv_as_dataframe with tabular_as_csv
- [18] DOWMLLib.get_output returns a dict instead of a list
- [16] 'output' stores files in subdirectories
- [12] Add 'shell' command in the Interactive