`shelly config create' should check if config already exists …

If it does, it will suggest using `shelly config edit` with appropriate
arguments and quit.

[#68558140]
`shelly config create` should ask to specify cloud

when there are multiple clouds in Cloudfile

[#68557874]
Merge pull request #128 from shellycloud/check-if-config-exists

`shelly config create' should check if config already exists, should ask to specify cloud