Transparent Interception remodelling.

This patch merges part 2 of the TPROXY-related updates.

 - Makes interception handling flags and options always-present
 - Updates squid.conf http_port options for clarity
 - Builds structure for sequential lookup of multiple interception methods
 - Performs sequential lookups for IPFW and multiple Netfilter targets
   if Squid configured to enable those transparency methods.
 - Pulls most of the TPROXYv2 related code out of Comm into IPInterception

IPFW changes are still experimental, but Netfilter targets have been tested.

TODO: depending on the anoyance levels a better logging method for NAT
      failures may need to be implemented. The existing methods of logging
      one-per-N seconds, for all lookup methods may prove annoying.