feat(registry): add login/logout commands

[Sh4d1]

Needs #909

[remyleone]

I get the following message:

$ go run ./cmd/scw/main.go registry  login   
{"message":"","error":{},"details":"","hint":"Valid arguments are: "}
Error saving credentials: error storing credentials - err: exit status 1, out: `{"message":"","error":{},"details":"","hint":"Valid arguments are: "}`
exit status 1

Could you indicate in a log message that you are using a precise executable?

$ go run ./cmd/scw/main.go registry  login --help
This command will run the correct command in order to log you in on the registry with the chosen program.
You will need to have the chosen binary installed on your system and in your PATH.

[jerome-quere]

LGTM