security/acme-client: Update to 0.1.13

• Update to 0.1.13
• Modify all configuration paths from letsencrypt to acme
• Update periodic script to reflect path changes
• Update sample scripts to reflect path changes
• Add warning to pkg-message for changed paths
• Add UPDATING entry for changed paths
• Remove warning for old periodic.conf variable names
• Remove warning for letskencrypt rename