Fix bad API_KEY handling.

[fhacloid]

There are a number of issue detected with the current handling of the API KEY:

• CLI seems to try to send the auth token of a parent org when making actions on a child org.
• CLI writes config with 0644 permissions on user's home which is bad (fix perm)
• If the config is empty, the CLI panics (bad errors handling and nil map assignment)
• We should allow (and recommend) to fill in the token via env var. Passing the token via arg will write it in the user's bash history.

Tasks

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1. Scope login to API URL
2. In the config file, split orgs by API URL
3. If the config is empty, the CLI panics (bad errors handling and nil map assignment)
4. CLI writes config with 0644 permissions on user's home which is bad (fix perm)
5. We should allow (and recommend) to fill in the token via env var or stdin. Passing the token via arg will write it in the user's bash history.
6. Org related token env
7. Fix current org selection via config / env var

[fhacloid]

@gaelL @talset @marcoldp Any suggestions on this one ?