Add api update command

[leoschwarz]

This will supersede the api save command which always directly wrote. It will also be more clear that if we add a create later. I think for the command line tools it's better to be more explicit about create vs update, to prevent user errors when the id is present or absent accidentally.

When using in scripts --no-confirm can be specified whereas it should prevent some more obvious problems when someone less experienced uses these scripts.