Polo configuration

• POLO_USER_DIR: The root folder for all polo parameters (services, configuration files, etc) (by default /etc/marcopolo/polo).
• SERVICES_DIR: The name of the directory relative to POLO_USER_DIR (by default ./services)
• MULTICAST_ADDR: The multicast groups to join.
• RETRIES: Maximum number of retries if no multicast joining can be done (due to a network failure).
• HOPS: Value of the TTL field in the messages (experimental).
• LOGGING_DIR: Directory for log storage.
• LOG_FILE: Name of the log file.