Bugfix: direction option was confusing because it was mixed with chains

Bugfix: direction option was confusing because it was mixed with chains

- Separate direction command into two separate commands: direction, and chain.
- The chain command mimics iptables chains and is automatically populated by the custom lists (aka: custom chains).
- When direction is set to something other than none, then the active ethernet device is used.
- Code cleanup and changes were performed while working on this.
- Added basic support for debugging, define _en_firewall_debug_ to enable custom debugging parameter.