Allow the crl-storer to load whole AWS config files. Although
this requires a deployment to maintain an additional config
files for the crl-storer, and one in a format we usually don't
use, it does give us lots of flexibility in setting up things like
role assumption.
Also remove the S3Region config flag, as it is now redundant
with the contents of the config file, and rename the existing
S3CredsFile config key to AWSCredsFile to better represent
its true contents.
Fixes#6308
Aaron Gable