Unsupport all protocols other than TCP and UDP
This patch updates the collector according to the server part of FWlogs which currently doesn't accept other network protocols than TCP and UDP (messages with unsupported protocols are dropped by the sanity check and cause emitting warnings).
Firewall events with unsupported protocols will emit debug messages and will not be sent to the server part.
This patch updates the unit tests to exclude ICMP/ICMPv6 messages (these ones will no longer be accepted).
Resolves #10.