Rafactoring ACL attributes

[mzbroch]

• [x] class refactor - distinguish between "actions" and ACL attributes , move "actions"/"settings" under ACL.Meta class
• [x] unittests
• [x] Cartesian product supports None values: src_ip': None, 'dst_ip': None, 'action': None}
• [ ] drop order_* methods
• [ ] option to raise exceptions in validate_
• [ ] aggregate results in validate_ and enforce_
• [x] remove dst_port processor,
• [ ] -- provide additional examples through docs or contrib
• [x] docs updates