Multiple configuration files via .d syntax

• Added: support for multiple configuration files using conf.d style directory. Only used in case legacy fw_fules.conf doesn't exist!
• Added: help + version info
• Added: systemd reload triggers firewall restart
• Changed: iptables bin location (within thor.conf) to /usr/sbin/iptables-nft
• Changed: License to Mozilla Public License 2.0 (MPL-2.0)