Change DB cart default to MySQL
Merge pull request #295 from nhr/switch_db_default

Change DB cart default to MySQL
Revise conf_broker_auth_private_key config

- Generate the public key from the private key
- Update the permissions on the private and public key
- Notify the broker service on auth key changes
- Remove conf_broker_auth_key_password
Merge pull request #296 from detiber/brokerAuthKey

Revise conf_broker_auth_private_key config