add default of signature check from QUILIBRIUM_SIGNATURE_CHECK env var

• add support for QUILIBRIUM_SIGNATURE_CHECK env var to set default value of -signature-check flag
• in Docker container remove explicitly set -signature-check=false and set it as env var
• add log message when signature check is disabled

This allows running node commands through docker compose exec without always having to add -signature-check=false, and have a consistent experience with docker containers that do not disable signature checking.