Add some tests for jaws.native.

Change credentials system not to load credentials at initialization time.
Calls to def-cred (new function), add-cred-file, or add-cred-files,
are required to replace the previous static lookup in a fixed location.

Improve diagnostics when we are unable to parse credentials.

Allow quoted credential values on the right of the equal (=) sign.

Allow specification of explicit credential files, not conforming to any
pre-existing pattern.

Split credential stuff in to creds.clj.

defcred becomes use-cred, and a new def-cred (note hyphen) comes into being.

Add 0 to reduce call to handle empty credential sequences in list-credentials.