add REPL command mismatch behaviour and documentation

[nicolamos]

The help for the add REPL command states the following syntax, if I understood correctly:

add <name> via <drivers>… from <source>

I ran this command: add postit via -sl passthrough from data/exp_raw/2022/2022-10-18/postit,
but then the word via is also used as a possible Storage or Loader, resulting in the following output:

! Failed to create 'via' Storage
 ! Failed to create 'passthrough' Storage
 ! Failed to create 'via' Loader
 ! Failed to create 'passthrough' Loader

[tecosaur]

Thanks for the issue Nicola, I hadn't noticed this discrepancy, but it would be good to make it behave as the docs describe.