By default for new accounts, use relative paths
for certificates, keys and archive.
Absolute paths are still supported.
This make it easier to move ring installs between
computers.

Change-Id: I5a34c8174225446e6b5d6cb17c05f147cdff0b5b
Reviewed-by: Guillaume Roguez <guillaume.roguez@savoirfairelinux.com>