Currently, Phabricator credentials are described by number.
This solution isn't the best for maintenance and doesn't allow secrets
replacement easily (what if we want to hunt the number 2 in the repo?).
This change provides a new pillar entry, zr_credentials, to map the IDs
to dictionary keys.
The Zemke-Rhyne execution module is updated to support keys expressions
(with . or : as separatator) in addition to numeric values.
The key dotted format has been selected to be stable, as the key would
also be a valid expression to fetch the secret in other stores, like Vault.