Add `load` command and swap places for the command with the plugin name

[BogdanIrimie]

We want to change the order of the commands for ds-load so that the command comes before the plugin name.
E.g.

ds-load fetch auth0 <- fetches data from idp and prints it to stdout
ds-load transform auth0 <- fetches data from stdin and outputs it to stdout
ds-load load auth0 <- fetches data from stdin and writes to directory
ds-load import auth0 <- fetches data from idp and writes it to directory. This command might have a --dry-run argument

[ronenh]

I don't think that in this model we'll have a ds-load load auth0 command. It will simply be ds-load load.
There's no dependence on plugins so it's not clear what the command would do with the auth0 argument.