You can now set credentials in environment variables.

To enable this we now look for credentials associated with the hostname only.
We fall back to using the the entire URL for backwards compatibility.

Also we needed to replace ALL `.` characters with `__`.
Add a note in the man page about periods in environment variables
Merge pull request #3295 from staugaard/only_use_hostname_for_credentials_lookup

You can now set credentials in environment variables.